Hey there tigershark.
It is in a way possible, but it requires some work and adjustments.
So you may be able using a 'backdoor'.
Lets say a unit has thunder clap, and you want a cooldown on it every 60 seconds.
First of all, you'd need to create a 'fake' dummy spell which deals no damage, no effects and has NO targets. Important is that this dummy spell should have all the same data of the original and the same cooldown (no mana cost!).
Then, you'd create a timer which runs each 60 seconds for example.
After these 60 seconds you'd replace the original with the dummy and make it instantly cast the dummy spell. Create a wait function which has the same amount of time like the cooldown of your choise. After the wait is done, simply replace the dummy with the original again.
Extra notes:
- I suggest you'd use an instant castable spell.
- To check if the cooldown is already running at those 60 seconds, make a boolean. Whenever you launch the original spell, set that boolean to true (false after the cooldown time, use wait), and make the timer check the boolean first.
I hope this helps you and could give you a possibly solution for your problem.
-Xarwin