Mozilla has added a useful new feature to their latest beta release. This new feature is named Reset Firefox and it does exactly that.
Reset Firefox would create a new profile for you while migrating some of the data from your original profile.
It would then delete the older profile and what you would have is a neat and clean installation of Firefox.
The developers spoke about the feature:
It only saves bookmarks, passwords, cookies and form data. You will lose your add-ons, Sync settings, open tabs and tab groups.
It only works with the default profile. If you’ve opened Firefox via the command line or shortcut with a profile that isn’t the default, you won’t see the Reset Firefox button.
This can save you the hassle of migrating specific content from one profile to another manually.