I just gave one of your extensions 1 star review, so here: this is what I've wanted for since AIO Sidebar went away with legacy extensions. I think it was the one that could show all the about: pages.

Does it have all of them? What about possible other similar stuff - I know there are some other URI beginnings, but don't know if their useful for this (like view-source:). But there might be more I don't know about.

Anyway, excellent!

A button that displays config pages, you can also access and bookmark

http://about:about

for the same result

about:about
about:addons
about:buildconfig
about:cache
about:checkerboard
about:config
about:crashes
about:credits
about:debugging
about:devtools
about:downloads
about:home
about:library
about:license
about:logo
about:memory
about:mozilla
about:networking
about:newtab
about:performance
about:plugins
about:policies
about:preferences
about:privatebrowsing
about:profiles
about:restartrequired
about:rights
about:robots
about:serviceworkers
about:studies
about:support
about:sync-log
about:telemetry
about:url-classifier
about:webrtc
about:welcome

Sad that yet another nice addon can't function properly because of Mozilla.
I think it would be nice if you change the greyed out menu entries to put the url on the clipboard.

Crippled through no fault of your own.
Idea is great
Gave it 3/5 because it is still handy for quickly seeing what is available for people unfamiliar with the browser.
If it ever linked to those pages it would be 5/5