your problem is with how windows defines "not in use".
you want the screen to turn off after 5 minutes of anything
except for reading in the viewer ?
your best bet may be to outwit it, find something it counts as " in use" like leaving a dialogue box open some where else on the screen.
but surely, if you create a desktop shortcut to control panel, then its only a couple of clicks to switch power plans between your usual one, and a copy that has screen off= never. toggle it as needed
someone a bit more skilled could probably shrink that to one click by having the relevant CMD commands saved as shortcuts. see here
https://docs.microsoft.com/en-us/win...d-line-options
so something like this sets the 5 minute value
powercfg /change monitor-timeout-ac 5
add a zero for a 50 minute option
powercfg /change monitor-timeout-ac 50