Hi,
It seems to be possible to use a widget (via an external automation) to simulate a motion sensor triggering, but it doesn’t seem to be possible to use a widget to disable a motion sensor entirely. Perhaps the easiest way to do this in the general case would be to add “disable or enable an automation” to the possible sets of actions an automation can do, and to make sure that both the general and sensor-specific automations show up in the resulting list. I can think of a few other use cases for this, too — for instance, turning off time-based color change automations when I have guests over.