Is this what you're looking for? I found out how to sort the pre-made replies alphabetically.
(I prefix the titles of my premade replies with things like "Billing" or "Technical"... so then the alphabetization helps a lot.)
Here's how:
http://osticket.com/forums/showthread.php?t=4921(http://osticket.com/forums/showthread.php?t=4921)