Firefox has a profile manager in
about:profiles. I created a new profile to troubleshoot compatibility issues, but absolutely everything including addons and
about:config entries was moved to the new profile.
I can't understand as this is the description on the page:
This page helps you to manage your profiles. Each profile is a separate world which contains separate history, bookmarks, settings and add-ons.
How to reset everything to the default in the new profile?