On Quest-line HMDs (Quest/Quest 2/Quest Pro), adb shell am broadcast -a com.oculus.vrpowermanager.prox_close disables the prox sensor until a reboot.
This performs the same function as putting tape over the prox sensor. When prox is disabled, the display only turns off when “Auto Sleep” is triggered after a period of non-motion. The Auto Sleep timeout can be modified by going to Settings->Power on the HMD.
Use at your own risk. Forcing the display to remain on for extended periods (multiple hours) can cause burn-in, and it will make the battery drain very fast. That said, disabling prox is often useful for development, specifically to avoid having to balance the damn thing on your head while you’re looking at code.