> I live and work in a multi-lingual environment, and have set up a keyboard shortcut to switch between the German and English keyboard. MacOS does not have a keyboard shortcut for this.

MacOS has since the early OS X days the default shortcut CTRL+Space for that. It may be deactivated for newer releases. It's findable under:

Settings → Keyboard → Keyboard Shortcuts → Inputsomething

(Einstellungen → Tastatur → Tastaturkurzbefehle → Eingabequellen)

Personally I dream of a Mac keyboard with OLED key caps for multilingual keyboard layouts.