How many devices do you have like that? Could you set up all your desired "global off" devices as a "Room" and turn off (on) the room?
I do not use the WM100 much, but recollect you can turn off (on) a "Room".
Probably set up the devices as a scene also, and then "Stop All" the scene but don't know if that will actually extinguish the lights. If you have multiple scenes, I guess that would not work.
Jus noodling.
