Ignore auto screen off when always screen on is active

During my last trip I had the problem, that the screen kept switching off, even though I had activated "always screen on - When charger is plugged in" and connected an external battery. After a while I figured out this was caused by the "auto screen turn-off" settings. After setting the auto turn-off time to 0 the display stayed on, as desired. But now it also stays on when no external power supply is attached, draining the internal battery.

So I would like to see that the auto turn-off time is ignored when "always screen on" is active.