Multiple Hotkeys for the same action?

Hey, someone aware of a method to bind multiple hotkeys for the same action?

For instance I'm using standard Grid to play, but would like to also bind palisade and gate to my mouse buttons. I checked for the HK-File, but its seems I'm not able to just edit that and add keys like in most games.

Only way I can currently think of is to make my mouse button in the driver to use the same key as e.g. palisade, not really a fan of that one for obvious reasons.