When I copy an action for pasting, the step numbers are in the format of "0001", "0002". I assume this means an action can have a maximum of 9999 steps? I couldn't see anything in the manual that mentions a limit.
Yes, the maximum is 9999 steps. Most actions are nowhere near that size so it's really just an arbitrary limit that was chosen. I once helped a user with an action they created and it was 313 steps; the biggest action I've seen to date.
I guess I could realistically lower the limit to 999 steps to save some resources (app memory), but I have no plans to do that. Keeping it future-proof is the better idea, IMO.
Good idea.