Example customization for handling a GetOptions style picker inside a struct.

JoePropertyCustomizations.cpp

#include "JoePropertyCustomizations.h"

#include "DetailWidgetRow.h"
#include "IDetailChildrenBuilder.h"
#include "PropertyCustomizationHelpers.h"
#include "SSearchableComboBox.h"

TSharedRef<IPropertyTypeCustomization> FJoeCustomStructPropertyCustomization::MakeInstance()
{
	return MakeShareable(new FJoeCustomStructPropertyCustomization);
}

void FJoeCustomStructPropertyCustomization::CustomizeHeader(TSharedRef<IPropertyHandle> StructPropertyHandle,
                                                            class FDetailWidgetRow& HeaderRow,
                                                            IPropertyTypeCustomizationUtils& StructCustomizationUtils)
{
	if (StructPropertyHandle->HasMetaData(FName(TEXT("ShowOnlyInnerProperties"))))
	{
		return;
	}

	HeaderRow.NameContent()
	[
		StructPropertyHandle->CreatePropertyNameWidget()
	]
	.ValueContent()
	[
		StructPropertyHandle->CreatePropertyValueWidget()
	];
}

void FJoeCustomStructPropertyCustomization::CustomizeChildren(TSharedRef<IPropertyHandle> StructPropertyHandle,
	class IDetailChildrenBuilder& ChildBuilder,
	IPropertyTypeCustomizationUtils& StructCustomizationUtils)
{
	//Change this to your struct and your name for the label property.
	TSharedPtr<IPropertyHandle> LabelHandle = StructPropertyHandle->GetChildHandle(GET_MEMBER_NAME_CHECKED(FJoeCustomStruct, Label));
	uint32 NumProperties = 0;
	StructPropertyHandle->GetNumChildren(NumProperties);
	for (uint32 i = 0; i < NumProperties; i++)
	{
		auto ChildHandle = StructPropertyHandle->GetChildHandle(i);
		if (ChildHandle->GetProperty() == LabelHandle->GetProperty())
		{
			//Special case the label parameter.
			auto NameWidget = LabelHandle->CreatePropertyNameWidget();
			ChildBuilder.AddCustomRow(LabelHandle->GetPropertyDisplayName())
				.NameContent()
				[
					LabelHandle->CreatePropertyNameWidget()
				]
				.ValueContent()
				.MinDesiredWidth(125.f)
				.MaxDesiredWidth(600.f)
				[
					SAssignNew(ComboBox, SSearchableComboBox)
					.OptionsSource(&Labels)
					.OnComboBoxOpening(this, &FJoeCustomStructPropertyCustomization::GenerateLabels, StructPropertyHandle)
					.OnGenerateWidget(this, &FJoeCustomStructPropertyCustomization::MakeItemWidget)
					.OnSelectionChanged_Lambda([=](const TSharedPtr<FString> NewChoice, ESelectInfo::Type SelectType)
								   {
									if(NewChoice).IsValid())
									{
										const FScopedTransaction Transaction(TEXT("Set Label Value"));
										LabelHandle->NotifyPreChange();
										LabelHandle->SetValue(*NewChoice);
										LabelHandle->NotifyPostChange(EPropertyChangeType::ValueSet);
									}
								   })
					.Content()
					[
						SNew(STextBlock)
						.Text_Lambda([=]()
							     	{
									FName CurrentValue = NAME_None;
							   		LabelHandle->GetValue(CurrentValue);
							     		FString CurrentValueString = CurrentValue.ToString();
						     			return FText::FromString(CurrentValueString);
								})
					]
				];
		}
		else
		{
			//Add any other parameters in the struct.
			ChildBuilder.AddProperty(ChildHandle.ToSharedRef());
		}
	}
}

void FJoeCustomStructPropertyCustomization::GenerateLabels(TSharedRef<IPropertyHandle> StructPropertyHandle)
{
	const TSharedPtr<IPropertyHandle> SUDSScriptHandle = StructPropertyHandle->GetChildHandle(GET_MEMBER_NAME_CHECKED(FJoeCustomStruct, SUDSScript));
	UObject* SUDSScriptPtr;
	const FPropertyAccess::Result Result = SUDSScriptHandle->GetValue(SUDSScriptPtr);
	Labels.Reset();
	if(Result == FPropertyAccess::Success)
	{
		if (USUDSScript* SUDSScript = Cast<USUDSScript>(SUDSScriptPtr))
		{
			//Early out if SUDSScript isn't set.
			if (!SUDSScript) return;
			
			TArray<FName> LabelNames = SUDSScript->GetLabels();
			Algo::Transform(LabelNames, Labels,[&](const FName& InLabel)
			{
				return MakeShared<FString>(InLabel.ToString());
			});
		}
	}

	if(ComboBox.IsValid())
		ComboBox->RefreshOptions();
}

TSharedRef<SWidget> FJoeCustomStructPropertyCustomization::MakeItemWidget( TSharedPtr<FString> StringItem ) 
{
	check( StringItem.IsValid() );

	return SNew(STextBlock)
		.Text(FText::FromString(*(StringItem.Get())));
}

JoePropertyCustomizations.h

#pragma once

#include "IPropertyTypeCustomization.h"

//Copy this into your Editor BeginModule:
//FPropertyEditorModule& PropertyModule = FModuleManager::LoadModuleChecked<FPropertyEditorModule>("PropertyEditor");
//PropertyModule.RegisterCustomPropertyTypeLayout(FJoeCustomStruct::StaticStruct()->GetFName(), FOnGetPropertyTypeCustomizationInstance::CreateStatic(&FJoeCustomStructPropertyCustomization::MakeInstance) );

//Copy this into your module includes into your Module Editor.Build.cs
//"ToolWidgets"

//This isn't needed, remove it when you remove the USUDSScript and the FJoeCustomStruct
#include "JoePropertyCustomizations.generated.h"

//Struct should exist in game code. not here.
//SUDSScript class is a stub.

class SSearchableComboBox;
class SWidget;

UCLASS(BlueprintType)
class USUDSScript : public UClass
{
	GENERATED_BODY()
public:
	UFUNCTION()
	TArray<FName> GetLabels()
	{
		return {FName(TEXT("A")), FName(TEXT("B")), FName(TEXT("C"))};
	}
};

USTRUCT(BlueprintType)
struct FJoeCustomStruct
{
	GENERATED_BODY()

	UPROPERTY(EditAnywhere, BlueprintReadWrite)
	TObjectPtr<UObject> SUDSScript = nullptr; //This would be your SUDSScript ref.

	UPROPERTY(EditAnywhere, BlueprintReadWrite)
	FName Label = NAME_None;
};

class IDetailLayoutBuilder; //Forward Declaration.

class FJoeCustomStructPropertyCustomization : public IPropertyTypeCustomization
{
public:
	static TSharedRef<IPropertyTypeCustomization> MakeInstance();

	virtual void CustomizeHeader(TSharedRef<IPropertyHandle> StructPropertyHandle, class FDetailWidgetRow& HeaderRow, IPropertyTypeCustomizationUtils& StructCustomizationUtils) override;
	virtual void CustomizeChildren(TSharedRef<IPropertyHandle> StructPropertyHandle, class IDetailChildrenBuilder& ChildBuilder, IPropertyTypeCustomizationUtils& StructCustomizationUtils) override;
	void GenerateLabels(TSharedRef<IPropertyHandle> StructPropertyHandle);
	TSharedRef<SWidget> MakeItemWidget( TSharedPtr<FString> StringItem );
private:
	TArray<TSharedPtr<FString>> Labels;
	TSharedPtr<SSearchableComboBox> ComboBox;
};