Allow multiple selection for modifier key to send

Modifier key selection allows you to set it either to be a ctrl, cmd, alt, shift or any. It would be nice if it can be set to multiple instead of one (e.g., cmd + ctrl).

That will allow to switch between windows and macos without breaking the OS defaults (win + ent to send isn’t a common pattern on windows, as well as ctrl + ent isn’t on macos).