Make it easy for SuperWhisper to take over the dictation key already present on Mac keyboards. That is the most obvious key to use to activate SuperWhisper. Might even be the best default.
(So far I have not been able to find any combination of settings to disconnect this key from the built-in dictation, which is useless compared to Super Whisper, other than to switch all of the keys to function key mode. but that disrupts use of a bunch of the other top row keys also.)