Group O Matic
Group O Matic makes it easier for the raid leader to set up the group arrangement. It can save and restore what groups people are in.
It also has an Auto button, which can push everyone to the top, or group melee together, or split the group into the odd/even group numbers, or other things. What the Auto button does is set by the "auto-arrange template" menu.
You can exclude the groups at the end of the raid from being changed, so that you can use those groups for bench/standby players (click More > Settings > Exclude groups).