Okey, now I think I understand what the problem is.
You see, unlike regular UObjects, AActors are expected to live within Game World.
To instantiate any subclass of AActor, use Spawn Actor from Class instead.
However, I belive your “Ability BP” is not suppoused to be something that actually lives in the Game World, right? If I understood correctly, it is only ment to hold some data (like atributes) and perform simple logic based on this data?
In this case, choosing the AActor as parent of this class is wrong, you should use UObject instead. Then using this node will be possible.
Still I’m not understanding the full concept behind this, so I’m maybe suggesting wrong here.