Not what I want. I want to be able to have distinct Firefox browser instances with each isolated from the other with its own bookmarks, extensions, settings, etc. The goal is to be able to have one independent browser for work, others for various personal technical projects, others for entertainment, and not have settings and tabs, etc, from any shared between them. Also to be able to have each independent Firefox browser open and running at the same time.
So basically multiple-accounts (browser preferences and everything) contained in independent browser instances.
Other than the benefit of keeping security isolated to each instance the other big gain for me would be de-cluttering, not having and seeing lots of tabs in one browser instance.

This add-on does not achieve either goal; no simple isolation at browser level, and still all that clutter as it is based around tabs.