I love this.

Tree Style Tab is THE reason I continue to use Firefox. It is a significant help in using the browser in an organized coherent fashion.
I have tried to use the roughly equivalent add-ons available for Chrome and Edge, and they are nowhere near as well designed.

Best tab sidebar, but can i use it without tree?

Really enjoy this plugin but why isn't the tree structure persisting when I restart Firefox and restore previous session?

Very useful. Clear and friendly interface. Greatly enhances Firefox, tab overview, bookmarks use.