What can you use Nova experience on?

I’m guessing the answer would be “nothing happens with the excess experience”.

For example: if you were to max out in any other thing/game/etc… you would still accrue points but it would just go to the bottom line total and do nothing from there. Pros/cons: pro, if there is ever an update to increase her max level cap, then everything you accrued after she was capped will/should push you into the new automatic level based on her bottom line experience that has accrued. Con: nothing happens until that cap is increased.

IMO there isn’t a con to her continually gain exp, however don’t waste resources on purchasing her EXP cards (stored in the bag) - as that is how I am currently spending resources to try to boost her levels (mine is at either 31 or 41… I forget).

It's used to level up Nova, once you have healed Nova in the Research Lab you can level her up which then raises the cap on various skills for military and economy buffs.

Tap on the research lab building and choose the Nova option then check the progress bar below Nova.