1. Create Instanced property

    	UPROPERTY(EditAnywhere, BlueprintReadWrite, Instanced, Category = "CategoryName")
    	UInstancedClassName* ClassName;
    
  2. Mark the class that should be DefaultToInstanced

    UCLASS(BlueprintType, Blueprintable, Abstract, EditInlineNew, DefaultToInstanced, CollapseCategories)
    class UInstancedClassName : public UObject
    {
    	GENERATED_BODY()
    
    };
    ****