Allowing secondary key(s) and/or mouse button(s) to be added to one of the select few Smart Action trigger keys or buttons would be incredibly useful.

For example, the ability to have different smart triggers for CALC + 1, CALC+ PageUp, Shift + Mouse Fwd. Button, all bound to different application-specific Smart Actions would greatly consolidate the keyboard real estate needed to efficiently execute repetitive actions. Much more conducive to building muscle memory and getting more density out of Smart Actions in general.