Touchbar button with swipe left/right gestures?

I was hoping to be able to set up a brightness control that:

  • was a single button
  • when touched, would allow swipe left/right
  • would adjust the brightness based on that swipe

As far as I can tell, this isn't possible: I could use the global gestures, but they don't support single finger swipe, and I don't think I can have that active if, and only if, I started by touching a specific button.

I'd appreciate if I missed something, if y'all could point me in the right direction?

I'm specifically looking for something that is one button "wide", doesn't open a new group, and doesn't use the "slider" format that the existing brightness widget, etc, do.

tagged feature request since I think this is not possible.