Add manual “Black Screen” button during foreground backup to reduce OLED burn-in, heat, and battery usage

[andrejhrasko]

I have searched the existing feature requests, both open and closed, to make sure this is not a duplicate request.

• Yes

The feature

Please add a manual button on the foreground backup screen to switch the display to a fully black screen while backup continues.

This is useful during large backups on OLED devices to reduce battery usage, heat, and screen wear.

Requirements

• user taps a button to enable it
• backup continues normally in the foreground
• device stays awake
• screen becomes completely black
• no persistent UI, text, progress, or overlays visible
• show only a brief toast when enabling it or when touching the screen, for example:
  “Black screen enabled. Double tap anywhere to exit.”
• exit by double tapping the screen
• after exit, return to the normal backup UI

This should be a manual, opt-in mode, not automatic dimming or automatic black-screen behavior.
Thanks :)

Platform

• Server
• Web
• Mobile

[bo0tzz]

We used to have auto dimming but removed it (#14791). We recommend turning down your screen brightness to the minimum manually.

[andrejhrasko]

I know there was this feature. The dimming might be nice but not necessary. This is about showing the total black overlay, so the OLED screen is totally off.
Synology Photos app has this feature (they call it "Focused backup") and it is nice since the full backup can take days.