A shift on another keyboard wouldn't work with the buddy tab key, right? Don't the modifier keys need to be on the same keyboard to function? I've always want

A shift on another keyboard wouldn't work with the buddy tab key, right? Don't the modifier keys need to be on the same keyboard to function? I've always wanted to map control/shift/alt/cmd to mouse buttons because I work a lot with a hand on the mouse, and some shortcuts are a bit hard one handed (ctrl+y) for example. I've tried to do this with programmable Logitech mice without success.