Hello,

I'm really sorry, but navigating to internal pages (like about:addons) or files on disk or other extensions pages is not possible anymore due to web-extension API restrictions.
See the note at the end of this page:
https://developer.mozilla.org/en-US/Firefox/The_about_protocol

I will put info about this into the description.

Have a nice day :)

Best regards,

Juraj Mäsiar