Turning the screen off when nobody looks saves energy and screen life. Changes are saved right away.
Turn the screen on or off right now. When the setting above has the screen off, ON wakes it for the screen timeout.
Restart MirrorDash takes a few seconds and is usually enough when something looks wrong. Restart Mirror restarts the whole Raspberry Pi (about a minute), needed after connecting sensors. Shut down before unplugging, so the SD card is never damaged. A button connected under Hardware can do the same.