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.
event_action;
Real
num = event_action;
The above code stores the current action number in the variable "num".