OnePlus
Volume Key Shortcut to Start Accessibility Feature auf OnePlus
The volume key shortcut on OnePlus phones lets you start one accessibility feature by pressing the volume buttons, without opening any app or menu. It only works once a service is assigned and the shortcut itself is switched on.
If nothing happens when you press the volume keys, either the shortcut is disabled or no service has been picked yet. If it works while the phone is unlocked but not from the lock screen, the lock screen permission for the shortcut is turned off separately.
How to enable or disable it
Go to Open the Settings ➔ Tap on System ➔ Tap on Accessibility ➔ Tap on Volume key shortcut. From here, Enable or disable Volume key shortcut turns the whole feature on or off.
Next, Tap on Shortcut service and Choose a Shortcut service from the list, for example TalkBack, Color Correction, Select to Speak or Switch Access. Then Tap on Back and use Enable or disable Allow from lock screen to decide whether the shortcut also works before you unlock the phone.
If you rely on TalkBack as your primary way to use the phone, keep the lock screen option enabled so you never get locked out of the shortcut.