Can you unlink action for multiple objects at once? I know you can right click object and select unlink action to do so.
Or do it inside action editor.
The question is this is too slow. There are so many actions there for different objects, what if you want to switch animation from one to the other. That would be a nightmare.
Is there anything I can look into? Thanks.
If you got actions objects spread in an object hierarchy. (but they use same action)
Yes, you can modify action of them all at once by script.

for loop that object hierarchy and see if object got action element. save them in list or something like that
hard coded script or make a panel to pick the action name.
assign the action you pick to those action objects you found.