If you have the "G-sensor" turned on, just reach over and give the cam a good tap with your fingers which should lock the current file. Test this before relying on it, as the force needed will vary. Easier to do quickly since you don't have to aim for a specific button where you might hit the wrong one instead
set the proximity sensor which is on the WiFi LED side to start a Manual recording when you cover that area with your hand.
Do that with the app via firmware settings