Browser: Opera 78.0.4093
OS: Mac OS X 10.15.7
Hey there,
german guy here, too. I just figured this out: ⌘+` is blocked for opening the settings tab. Just go to Einstellungen ➡ Schnellzugriff and remove the shortcut in setting Einstellungen öffnen. Afterwards the toggle is working fine (coming from Chrome this really annoyed me).