I've noticed that each time I get a grapheneos update, the device control shortcut get reset/removed.
Those are available from tho notification panel. You can also add them to your lockscreen by going to Settings->Display->Lock screen->Shortcut and select device control.
Also, as I just reconfigured the commands, it seems that you need a full reboot so that you can add the device control to tho lock screen. Otherwise even if you register new control, the app does not recognize you having added any. Anyone has a trick to fix this ? it’s not very important so I don’t think it’s worth bothering the devs about that. Maybe it’s just a setting or a piece missing in the update packages that resets the controls.