It’s in KismetSystemLibrary.h (Engine\Source\Runtime\Engine\Classes\Kismet)
UKismetSystemLibrary::MoveComponentTo(USceneComponent* Component, FVector TargetRelativeLocation, FRotator TargetRelativeRotation, bool bEaseOut, bool bEaseIn, float OverTime, TEnumAsByte<EMoveComponentAction::Type> MoveAction, FLatentActionInfo LatentInfo);
In general, if you have the source you can do “Find In Files”, then the name of the blueprint node without whitespaces (in this case “MoveComponentTo”), set Look In to “Entire Solution” and tell it to search in all *.h files (under “Find options”). The name of whatever default blueprint node you want should come up. Most convenience functions like the one you were searching for will be in the KismetSystemLibrary.