Boilerplate UBlueprintFunctionLibrary in Unreal Engine 5 C++

// MyBlueprintFunctionLibrary.h file

#pragma once

#include "CoreMinimal.h"
#include "Kismet/BlueprintFunctionLibrary.h"
#include "MyBlueprintFunctionLibrary.generated.h"

/**
 * 
 */
UCLASS()
class TESTING_API UMyBlueprintFunctionLibrary : public UBlueprintFunctionLibrary
{
	GENERATED_BODY()
	
};

// MyBlueprintFunctionLibrary.cpp file

#include "MyBlueprintFunctionLibrary.h"

Useful Example:

#pragma once

#include "CoreMinimal.h"
#include "Kismet/BlueprintFunctionLibrary.h"
#include "MyBFL.generated.h"


UCLASS()
class TESTING_API UMyBFL : public UBlueprintFunctionLibrary {
    GENERATED_BODY()

   public:
    UFUNCTION(BlueprintCallable, BlueprintPure)
    static int Add(int A, int B){
        return A + B;
    }

    UFUNCTION(BlueprintCallable)
    static void AddTo(UPARAM(ref) int &A, int B){
        A += B;
    }
};

References:

• Pobato Tutorials - Blueprint Function Library in C++ for Unreal Engine in 2 Minutes!