how to reuse app specific password

A couple of questions re app specific passwords (asp's)

how do you reuse one? apple only allows 25 (granted, I haven't reached that limit). I created one for Airmail app on my MacBook. How do I access and use it on my iMac? I can see in the asp history, but no way to copy it? do I need separate ones for each Mac I own? what about on iOS? since apple only grants 25 asp's at a time, using 3 (or more) of them for one app on all my computers (MacBook Pro, iMac, iPhone, and 2 iPads) seems wasteful.

Or, am I misunderstanding something?

Thanks