Header file for later versions of Unreal (currently 4.21.1)

[ChocoBilly]

I had to add

#include "Classes/Kismet/GameplayStatics.h"

to make sure that

UGameplayStatics::SuggestProjectileVelocity(
		this,
		OutLaunchVelocity,
		StartLocation,
		HitLocation,
		LaunchSpeed,
		false,
		0.0,
		0.0,
        ESuggestProjVelocityTraceOption::DoNotTrace
		);

Will show up in intellisense. Just FYI if you’re having problems.