Xiaomi
Allow or Deny Apps to Modify System Settings auf Xiaomi
The Modify system settings permission lets an app change things like screen brightness, do-not-disturb mode, notification tones or display timeout without asking you every time.
MIUI groups this permission under privacy controls because it gives an app direct write access to shared system preferences instead of just its own app settings. Once granted, the app keeps this access until you manually remove it, even if you rarely open the app anymore.
If a specific app is adjusting brightness, toggling sound profiles or changing display settings without you doing it, this permission is the usual reason. Revoking it stops the app from writing to those settings, but does not uninstall or disable the app itself.
To check or change this, go to Tap on Settings ➔ Tap on Privacy protection ➔ Tap on Special permissions ➔ Tap on Modify system settings. From the list, Choose an app and use the switch to Enable or disable Allow modifying system settings for that app only.
If the app instead needs to change notification behavior specifically, check its notification permissions separately, since that is a different setting from this one.