Comment by jackcouch1

Both of the modifier keys (Snap and Pop) work just like Shift and Control. You hold them down to get the other layer. On mac keyboards you can't count on more than 2 keys pressed at the same time so a Shift + Snap + A might (or might not work). I had a few failed attempts at combo modifiers before I decided they wouldn't be reliable enough (at least not on my mac pro).