ue-editor-tools

name	ue-editor-tools
description	Use when extending the Unreal Editor with editor tool, editor utility widget, Blutility, detail customization, property customization, editor mode, asset editor, editor subsystem, editor extension, UToolMenus, or scripted asset operations. For Slate fundamentals, see ue-ui-umg-slate. For module build config, see ue-module-build-system.
metadata	{"version":"1.0.0"}

UE Editor Tools

You are an expert in extending the Unreal Editor with custom tools and workflows.

Context

Read .agents/ue-project-context.md for editor module structure, engine version, team workflows, and project-specific conventions before providing guidance.

Before You Start

Ask which area the user needs if not clear:

• Editor Utility Widget — UMG panel run from editor right-click
• Blutility — UAssetActionUtility or UActorActionUtility scripted actions
• Detail Customization — Custom property panel (IDetailCustomization / IPropertyTypeCustomization)
• Custom Editor Mode — Viewport mode with specialized interaction (FEdMode)
• Asset Type Actions — Content Browser integration for a custom asset type
• Editor Subsystem — Editor-lifetime singleton (UEditorSubsystem)
• Menu / Toolbar Extension — UToolMenus additions to main menu, toolbars, context menus

---

Editor Module Setup

All editor-extending code must live in a module with "Type": "Editor". Never put UnrealEd / PropertyEditor includes in a Runtime module without #if WITH_EDITOR guards.

{ "Name": "MyGameEditor", "Type": "Editor", "LoadingPhase": "PostEngineInit" }

// MyGameEditor.Build.cs — key dependencies
PrivateDependencyModuleNames.AddRange(new string[] {
    "Core", "CoreUObject", "Engine", "UnrealEd",
    "Slate", "SlateCore", "EditorStyle",
    "PropertyEditor",   // IDetailCustomization, IPropertyTypeCustomization
    "EditorSubsystem",  // UEditorSubsystem
    "Blutility",        // UEditorUtilityWidget, UAssetActionUtility
    "ToolMenus",        // UToolMenus
    "AssetTools",       // FAssetTypeActions_Base
    "MyGame"
});

Module skeleton — every registration in StartupModule must be mirrored in ShutdownModule:

IMPLEMENT_MODULE(FMyGameEditorModule, MyGameEditor)

void FMyGameEditorModule::StartupModule()
{
    FPropertyEditorModule& PropMod =
        FModuleManager::LoadModuleChecked<FPropertyEditorModule>("PropertyEditor");
    PropMod.RegisterCustomClassLayout(
        UMyDataAsset::StaticClass()->GetFName(),
        FOnGetDetailCustomizationInstance::CreateStatic(
            &FMyDataAssetCustomization::MakeInstance));
    PropMod.NotifyCustomizationModuleChanged();

    UToolMenus::RegisterStartupCallback(
        FSimpleMulticastDelegate::FDelegate::CreateRaw(
            this, &FMyGameEditorModule::RegisterMenus));
}

void FMyGameEditorModule::ShutdownModule()
{
    if (FModuleManager::Get().IsModuleLoaded("PropertyEditor"))
    {
        FModuleManager::GetModuleChecked<FPropertyEditorModule>("PropertyEditor")
            .UnregisterCustomClassLayout(UMyDataAsset::StaticClass()->GetFName());
    }
    UToolMenus::UnRegisterStartupCallback(this);
    if (UToolMenus* TM = UToolMenus::TryGet()) { TM->UnregisterOwner(this); }
}

Full boilerplate with asset type actions, editor modes, and factory: references/editor-module-setup.md

---

Editor Utility Widgets

UEditorUtilityWidget (from EditorUtilityWidget.h) extends UUserWidget for editor-only UMG panels. Create as a Blueprint subclass (right-click Content Browser > Editor Utilities > Editor Utility Widget). Run: right-click the widget asset > Run Editor Utility Widget. Or subclass in C++:

#pragma once
#include "EditorUtilityWidget.h"
#include "MyEditorUtilityWidget.generated.h"

UCLASS()
class MYGAMEEDITOR_API UMyEditorUtilityWidget : public UEditorUtilityWidget
{
    GENERATED_BODY()
public:
    UFUNCTION(BlueprintCallable, Category = "My Tools")
    void BatchRenameSelectedAssets(const FString& Prefix);
};

// .cpp
void UMyEditorUtilityWidget::BatchRenameSelectedAssets(const FString& Prefix)
{
    for (UObject* Asset : UEditorUtilityLibrary::GetSelectedAssets())
    {
        if (Asset)
        {
            const FString Src = Asset->GetOutermost()->GetName(); // e.g. /Game/Folder/OldName
            UEditorAssetLibrary::RenameAsset(Src, FPaths::GetPath(Src) / Prefix + TEXT("_") + Asset->GetName());
        }
    }
}

Key UEditorUtilityLibrary functions (from EditorUtilityLibrary.h):

Function	Purpose
GetSelectedAssets()	Currently selected Content Browser assets
GetSelectedAssetsOfClass(UClass*)	Filter selection by class
UEditorAssetLibrary::DeleteAsset(Path)	Delete asset; RenameAsset for move/rename
GetSelectionSet()	Selected level actors
SyncBrowserToFolders(TArray<FString>)	Sync content browser view

Content browser filters: Use FARFilter with IAssetRegistry::GetAssets for programmatic asset queries by class, path, or tags.

Open a widget programmatically:

GEditor->GetEditorSubsystem<UEditorUtilitySubsystem>()
    ->SpawnAndRegisterTab(LoadObject<UEditorUtilityWidgetBlueprint>(
        nullptr, TEXT("/Game/EditorWidgets/BP_MyTool")));

---

Blutility: Scripted Actions

UAssetActionUtility — Asset Right-Click Actions

Any UFUNCTION(CallInEditor) on a UAssetActionUtility subclass appears in the Content Browser context menu. Set SupportedClasses in Class Defaults to filter by asset type.

#pragma once
#include "AssetActionUtility.h"   // Engine/Source/Editor/Blutility/Classes/AssetActionUtility.h
#include "MyAssetActionUtility.generated.h"

UCLASS()
class MYGAMEEDITOR_API UMyAssetActionUtility : public UAssetActionUtility
{
    GENERATED_BODY()
public:
    UFUNCTION(CallInEditor, Category = "My Tools")
    void SetTextureCompressionToUI()
    {
        for (UObject* Asset : UEditorUtilityLibrary::GetSelectedAssets())
        {
            if (UTexture2D* Tex = Cast<UTexture2D>(Asset))
            {
                Tex->CompressionSettings = TC_EditorIcon;
                Tex->MarkPackageDirty();
                Tex->PostEditChange();
            }
        }
    }
};

UActorActionUtility — Actor Right-Click Actions

Same pattern for level actors. Both UAssetActionUtility and UActorActionUtility inherit from UEditorUtilityObject, the base class for all Blutility actions.

---

Detail Customizations

Class Customization — IDetailCustomization

class FMyDataAssetCustomization : public IDetailCustomization
{
public:
    static TSharedRef<IDetailCustomization> MakeInstance();
    virtual void CustomizeDetails(IDetailLayoutBuilder& DetailBuilder) override;
    // Override the TSharedPtr overload too — store WeakBuilder for async ForceRefreshDetails
    virtual void CustomizeDetails(const TSharedPtr<IDetailLayoutBuilder>& DetailBuilder) override;
private:
    TWeakPtr<IDetailLayoutBuilder> WeakBuilder;
};
// In CustomizeDetails: EditCategory, AddProperty, AddCustomRow, HideCategory
// Register: PropMod.RegisterCustomClassLayout(UMyClass::StaticClass()->GetFName(), ...MakeInstance)
// Unregister in ShutdownModule: PropMod.UnregisterCustomClassLayout(...)

Struct Customization — IPropertyTypeCustomization

class FMyStructCustomization : public IPropertyTypeCustomization
{
public:
    static TSharedRef<IPropertyTypeCustomization> MakeInstance();
    virtual void CustomizeHeader(TSharedRef<IPropertyHandle> Handle,
        FDetailWidgetRow& HeaderRow, IPropertyTypeCustomizationUtils& Utils) override;
    virtual void CustomizeChildren(TSharedRef<IPropertyHandle> Handle,
        IDetailChildrenBuilder& ChildBuilder, IPropertyTypeCustomizationUtils& Utils) override;
};
// Register: PropMod.RegisterCustomPropertyTypeLayout(FMyStruct::StaticStruct()->GetFName(), ...MakeInstance)

Full implementations, Slate row patterns, IPropertyHandle read/write, NameContent/ValueContent: references/detail-customization-patterns.md

---

Custom Editor Modes

FEdMode (from EdMode.h) provides specialized viewport interaction. Register globally; only one active per viewport at a time.

// MyEditorMode.h
class FMyEditorMode : public FEdMode
{
public:
    static const FEditorModeID EM_MyMode;
    FMyEditorMode();
    virtual void Enter() override;
    virtual void Exit() override;
    virtual bool HandleClick(FEditorViewportClient*, HHitProxy*,
        const FViewportClick&) override;
    virtual bool MouseMove(FEditorViewportClient* ViewportClient,
        FViewport* Viewport, int32 X, int32 Y) override;
    // Use View->DeprojectFVector2D (FSceneView) for world-space ray from pixel coords
    virtual void Render(const FSceneView*, FViewport*,
        FPrimitiveDrawInterface*) override;
    virtual bool UsesToolkits() const override { return true; }
};

// MyEditorMode.cpp
const FEditorModeID FMyEditorMode::EM_MyMode = TEXT("EM_MyEditorMode");

FMyEditorMode::FMyEditorMode()
{
    Info = FEditorModeInfo(EM_MyMode,
        FText::FromString("My Editor Mode"), FSlateIcon(), /*bVisible=*/true);
}

void FMyEditorMode::Enter()
{
    FEdMode::Enter();
    if (!Toolkit.IsValid())
    {
        Toolkit = MakeShareable(new FMyEditorModeToolkit);
        Toolkit->Init(Owner->GetToolkitHost());
    }
}

void FMyEditorMode::Exit()
{
    if (Toolkit.IsValid())
        FToolkitManager::Get().CloseToolkit(Toolkit.ToSharedRef());
    FEdMode::Exit();
}

void FMyEditorMode::Render(const FSceneView* View, FViewport* Viewport,
    FPrimitiveDrawInterface* PDI)
{
    FEdMode::Render(View, Viewport, PDI);
    DrawWireSphere(PDI, FVector::ZeroVector, FLinearColor::Green, 50.f, 16, SDPG_World);
}

Register/unregister in module lifecycle:

// StartupModule
FEditorModeRegistry::Get().RegisterMode<FMyEditorMode>(
    FMyEditorMode::EM_MyMode, FText::FromString("My Mode"), FSlateIcon(), true);
// ShutdownModule
FEditorModeRegistry::Get().UnregisterMode(FMyEditorMode::EM_MyMode);

---

Asset Type Actions

FAssetTypeActions_Base (from AssetTypeActions_Base.h) controls Content Browser appearance and context menu for custom asset types.

class FMyAssetTypeActions : public FAssetTypeActions_Base
{
public:
    virtual FText GetName() const override { return FText::FromString("My Asset"); }
    virtual FColor GetTypeColor() const override { return FColor(200, 100, 50); }
    virtual UClass* GetSupportedClass() const override { return UMyAsset::StaticClass(); }
    virtual uint32 GetCategories() override { return EAssetTypeCategories::Misc; }

    virtual void OpenAssetEditor(const TArray<UObject*>& InObjects,
        TSharedPtr<IToolkitHost> EditWithinLevelEditor) override
    {
        for (UObject* Obj : InObjects)
            if (UMyAsset* Asset = Cast<UMyAsset>(Obj))
                MakeShareable(new FMyAssetEditor)->InitMyEditor(
                    EToolkitMode::Standalone, EditWithinLevelEditor, Asset);
    }
};

Register in StartupModule, keep reference, unregister in ShutdownModule.

FAssetEditorToolkit — Tab-Based Asset Editor Window

class FMyAssetEditor : public FAssetEditorToolkit
{
public:
    void InitMyEditor(EToolkitMode::Type Mode, TSharedPtr<IToolkitHost> Host, UMyAsset* Asset);
    virtual FName GetToolkitFName() const override { return "MyAssetEditor"; }
    virtual FText GetBaseToolkitName() const override { return INVTEXT("My Asset Editor"); }
    virtual void RegisterTabSpawners(const TSharedRef<FTabManager>& TabMgr) override;
    virtual void UnregisterTabSpawners(const TSharedRef<FTabManager>& TabMgr) override;
};
// Call InitAssetEditor() inside InitMyEditor to set up the tab layout via FTabManager::NewLayout

Query open editors programmatically via IAssetEditorInstance:

IAssetEditorInstance* Editor = GEditor->GetEditorSubsystem<UAssetEditorSubsystem>()
    ->FindEditorForAsset(MyAsset, /*bFocusIfOpen=*/false);
if (Editor) Editor->FocusWindow(MyAsset);  // CloseWindow(EAssetEditorCloseReason::AssetEditorHostClosed) — no-arg form deprecated 5.3

Asset Factories

UFactory subclasses allow the Content Browser's "Add" menu to create new custom assets:

UCLASS()
class UMyDataFactory : public UFactory
{
    GENERATED_BODY()
public:
    UMyDataFactory()
    {
        SupportedClass = UMyDataAsset::StaticClass();
        bCreateNew = true;       // appears in "Add" menu
        bEditAfterNew = true;    // opens editor after creation
    }
    virtual UObject* FactoryCreateNew(UClass* InClass, UObject* InParent,
        FName InName, EObjectFlags Flags, UObject* Context,
        FFeedbackContext* Warn) override
    {
        return NewObject<UMyDataAsset>(InParent, InClass, InName, Flags);
    }
};

Custom Thumbnails

UCLASS()
class UMyThumbnailRenderer : public UThumbnailRenderer
{
    GENERATED_BODY()
    virtual void Draw(UObject* Object, int32 X, int32 Y, uint32 Width, uint32 Height,
        FRenderTarget* Target, FCanvas* Canvas, bool bAdditionalViewFamily) override;
};
// Register in module startup:
UThumbnailManager::Get().RegisterCustomRenderer(UMyDataAsset::StaticClass(),
    UMyThumbnailRenderer::StaticClass());

---

Editor Subsystems

UEditorSubsystem (from EditorSubsystem.h) — editor-lifetime singletons, auto-discovered (no registration needed). Access via GEditor->GetEditorSubsystem<T>().

UCLASS()
class MYGAMEEDITOR_API UMyEditorSubsystem : public UEditorSubsystem
{
    GENERATED_BODY()
public:
    virtual void Initialize(FSubsystemCollectionBase& Collection) override
    {
        Super::Initialize(Collection);
        FEditorDelegates::PostUndoRedo.AddUObject(this, &UMyEditorSubsystem::OnPostUndoRedo);
    }
    virtual void Deinitialize() override
    {
        FEditorDelegates::PostUndoRedo.RemoveAll(this);
        Super::Deinitialize();
    }
};

Built-in subsystems:

Subsystem	Purpose
UEditorActorSubsystem	Select, spawn, delete level actors
UEditorAssetSubsystem	Load, save, duplicate assets
ULevelEditorSubsystem	Open, save, manage levels
UEditorUtilitySubsystem	Spawn editor utility widget tabs

---

Menu and Toolbar Extensions (UToolMenus)

UToolMenus (UE5+) replaces FExtender. Register inside the startup callback so Slate is ready:

void FMyGameEditorModule::RegisterMenus()
{
    FToolMenuOwnerScoped OwnerScoped(this);

    // Main menu
    UToolMenu* Menu = UToolMenus::Get()->ExtendMenu("LevelEditor.MainMenu.Window");
    Menu->FindOrAddSection("MyGame").AddMenuEntry("OpenMyPanel",
        FText::FromString("My Panel"), FText::GetEmpty(),
        FSlateIcon(FAppStyle::GetAppStyleSetName(), "Icons.Settings"),
        FUIAction(FExecuteAction::CreateLambda([]() {
            GEditor->GetEditorSubsystem<UEditorUtilitySubsystem>()
                ->SpawnAndRegisterTab(/* WidgetBP */nullptr);
        })));

    // Toolbar button
    UToolMenu* TB = UToolMenus::Get()->ExtendMenu(
        "LevelEditor.LevelEditorToolBar.PlayToolBar");
    TB->FindOrAddSection("MyTools").AddEntry(
        FToolMenuEntry::InitToolBarButton("MyBtn",
            FUIAction(FExecuteAction::CreateLambda([]() {})),
            FText::FromString("My Tool"), FText::GetEmpty(),
            FSlateIcon(FAppStyle::GetAppStyleSetName(), "Icons.Toolbar.Settings")));
}

Always unregister: UToolMenus::UnRegisterStartupCallback(this) + TryGet()->UnregisterOwner(this).

Command Registration — TCommands Pattern

class FMyCommands : public TCommands<FMyCommands>
{
public:
    FMyCommands() : TCommands("MyEditor", INVTEXT("My Editor"), NAME_None, FAppStyle::GetAppStyleSetName()) {}
    virtual void RegisterCommands() override;
    TSharedPtr<FUICommandInfo> OpenPanel;
};
void FMyCommands::RegisterCommands()
{
    UI_COMMAND(OpenPanel, "My Panel", "Opens the panel", EUserInterfaceActionType::Button, FInputChord());
}
// In StartupModule: FMyCommands::Register(); bind via CommandList->MapAction(...)
// In ShutdownModule: FMyCommands::Unregister();

---

Data Validation

// UEditorValidatorBase — auto-discovered by Editor > Tools > Validate Assets
UCLASS()
class UMyValidator : public UEditorValidatorBase
{
    GENERATED_BODY()
    virtual bool CanValidateAsset_Implementation(const FAssetData& InAssetData, UObject* InObject, FDataValidationContext& InContext) const override
    { return InObject && InObject->IsA<UMyDataAsset>(); }
    virtual EDataValidationResult ValidateLoadedAsset_Implementation(
        const FAssetData& InAssetData, UObject* InAsset, FDataValidationContext& Context) override;
};
// Also runnable via commandlet: UnrealEditor-Cmd -run=DataValidation

---

Common Mistakes

Mistake	Fix
Editor headers in Runtime modules	Move to Editor module; use #if WITH_EDITOR for runtime-side editor hooks
No UnregisterCustomClassLayout in ShutdownModule	Always pair register/unregister; crashes Live Coding reload
Raw pointer capture in Slate lambdas	Capture as TWeakPtr; pin before use
LoadingPhase: Default for editor extension module	Use PostEngineInit for modules registering menus or customizations
UEditorUtilityWidget referenced from Runtime	Editor-only; will not exist in packaged builds
ForceRefreshDetails() on every value change	Use only when layout structure changes; use handles/attributes for values
RegisterMode without UnregisterMode	Crashes on plugin reload

---

Related Skills

• ue-ui-umg-slate — Slate widget fundamentals (SNew, TAttribute, FReply, SBox, SHorizontalBox)
• ue-module-build-system — Editor module .Build.cs, LoadingPhase, WITH_EDITOR guards
• ue-data-assets-tables — Custom UDataAsset types that need asset editors and type actions
• ue-cpp-foundations — UPROPERTY, UFUNCTION, UObject reflection system