Edit 2020-09-24:
Thank you. Now it works! I didn't know that there was a way to change the shortcuts for extensions. I assumed that it is not possible because there is no option to change Firefox' own shortcuts.

Hi. I really like this addon, but since I don't use a US keyboard, I can't get all of the keyboard shortcuts to work. The rotate and mirror shortcuts don't work. All others do (moving and zooming). Can you please look into that? I'm using a german qwertz keyboard.
Thanks and keep up the good work!