Hello @dichi
if I needed a external power button for the M5Tough I'd solder a thin wire to GND and another to the existing power button; then connect the two wires to the external power button.
[image: 1686774453121-m5toughpowerbutton_20230614.png]
Optionally you could drill a hole into the base where the existing power button is. (You'd loose some water proofing I guess.)
Thanks
Felix