Has anyone noticed that the Setup button (button_status) event does not fire while in Listening mode? (blue blink)
I was thinking about using this as a convenient way to cancel setup, but it does not fire the event in user code even when SYSTEM_THREAD(ENABLED) is used.
It's quite possible that the button handlers are not hooked up in Listening Mode, but with an interrupt or in loop() via digitalRead(BTN) you should be able to work around this.
IIRC there also is another thread that was dealing with this.
As it seems there is no solution yet, but maybe opening an issue in the GitHub repo might be an idea.