This single extension is most of the reason I use FF as my daily driver. Can't live without it anymore. Being able to build out a tree, rearrange the subtrees,

This single extension is most of the reason I use FF as my daily driver. Can't live without it anymore. Being able to build out a tree, rearrange the subtrees, close out whole subtrees at once and have history maintained on each tab has ended up being central to my whole browsing flow.