How to assign a key to press Ctrl twice?

I'm trying to assign a key to function like the built-in "Siri" key on a MacBook Pro, where a tap launches dictation and a long press activates Siri.

Since I can't find "dictation" in the action menu, I wonder if it's possible to assign "Ctrl" pressed twice for this action. I've tried, but haven't had any luck. Any help would be appreciated.

I'm afraid that the modifier key Ctrl (⌃) can not be used as requested. You could use a key combo like Alt-S

You can set a shortcut for siri in system settings. Afterward you can set up a key sequence for double ctrl in BTT and make this key sequence trigger that shortcut: