As title says, this would be really convenient.

While you can add peers one at a time, there does not appear to be a way to add a list of peers, if that is specifically what you are requesting be added..

And it appears adding them is temporary.

See the description under the Peers section: http://support.tixati.com/transfer%20properties%20-%20options

Prior discussions:
http://forum.tixati.com/support/1074/
http://forum.tixati.com/support/1205/
http://forum.tixati.com/support/2178/

Yeah, adding a list of peers is what I want.

It's useful in cases where you're using magnet links with a proxy that lacks UDP. So if you have a list of peers, it will take a while until one shows up that is both online and has PEX. This is mostly a problem because the peers are not stored persistently like you said, and so adding them one at a time can be tedious.