Using Mavic pro Style Goggles standalone

I have one of those old DJI goggles from my Mavic Pro. I was able to use it as an HDMI device for my underwater camera for ice fishing. I would like to know how to activate a video capture or at least a screen capture when the Mavic Pro is not connected. Somehow, I managed to trigger a screen capture, but it was totally an accident and I have no idea what finger strokes on the touch pad. I did not have a micro sim in the goggles at the time.

You should be able to take a screenshot by tapping and holding the touch panel.