As if feature requests get added because we aren't lazy, lol
Anyway, PgUp/Down is already used as a shortcut to scroll the chat (which keep in mind is always opened while searching for a multiplayer room) so it wouldn't hurt to have it doing the same for the multiplayer rooms. You'll just need to not have the cursor above the chat (as it is now with the volume for the mousewheel) and it should work I guess