I researched it briefly, at that time it was not possible. There are lots of attempts to be "good enough" at tab management to make surviving without tree tabs

I researched it briefly, at that time it was not possible. There are lots of attempts to be "good enough" at tab management to make surviving without tree tabs possible. Some of them come close, most don't. At the end of the day, I changed my workflow to work with Chrome, rather than vice-versa because I found Chrome's responsiveness more valuable than Firefox's plugins.