Right now, Yahoo won't let me edit the Waiver Priority list. It has a link for it in the commish tools area, but the link is not active. I suspect that I will be able to edit the waiver priority once we finalize all the rosters and I activate the league, but I am not 100% sure this is how it will be. I've looked all over Yahoo and the web for confirmation, but no luck so far. I've also PM'ed Chris8, the commish of Pond Scum, to see if they have bumped up against this question. Have also PM'ed Fantasybaseballgenie, who works for Yahoo Fantasy and posts here on the Cafe.
Will get back to you when I find the answer.