This read-only variable returned the index of the action
currently being executed, starting at 0 on previous versions of
GameMaker. However, this is now an obsolete function in
GameMaker Studio 2. It has been left in for legacy support
only, and will always return 0 as all actions are
concatenated together to improve execution speed.
num = event_action;
The above code stores the current action number in the variable "num".