"alt+[" "alt+]" doesn't work (German keyboard)

I need the short cut for rotating an object by single degrees. With this I would be able to configure a rotating knob on a special device to do this job.

I found the short cut "Alt + [" and "Alt + ]" on https://inkscape.org/doc/keys092.de.html#idm2137. But it did not work with Inkscape 0.92 and still does not work with 1.0beta1. I use macOS 10.14. The option key seems fine. I am able to type those brackets in a text-window within Inkscape and I can use alt for selecting a hidden object.

However, this shortcut is listed on the mentioned web site only. It is not shown in the short cut section of the preference panel in the app (both versions). There is "rotate by 90 degrees" only.