I have foot pedal ctrl and alt keys. One set at home, one at the office. Some guitar pedals wired as momentary switches wired to a teensy. It's been using it for so long I forget they are there. I haven't even checked on the teensy since I can remember. I instinctive tape my feet even if I'm working away from my desk. If I'm zoned in I can even stamp my foot as though the pedal has become unresponsive... I don't use…
What software do you use to make this work? What OS?
On Windows it just works \tm.
The teensy using the keyboard library just holds ctrl or alt for the duration.
Linux is more finiticky but xkb lets you do the same (Linux or x or whatever seems to track which keyboard is which and doesn't mix inputs).
No idea bout Mac.