There's a rare incompatibility with Simple Tab Groups (->STG).
When saving a session in STG, the tree structure of Tree Style Tab (->TST) get lost completely and as a result the stucture is gone.
This happens on :
Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0
OS Linux 6.1.0-7-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.20-2 (2023-04-08)
OS Theme
and is a quite new problem.
Unfortunately I have no real idea how to check, which of both AddOn's produce the "error"...
Does anybody have an idea?
BTW... the rating will be reset after solving the issue, because I know this AddOn since a long time now and used it many times... sometimes in the past though it came to my attention, rhat there were some incompatibilities from time to time - that's why I post this message here and in STG.

I coundn't live without it during years. But now, Too much reported bugs that never get fixed, too much CPU & RAM hog, need to install TST addons, with reported bugs that never get fixed.

SideBery is way better, and stable !

Once you get used to you can't go back to using old style tabs. Althought it is not recommended to use this without the tab bar, after using it like that more then one year i can say it is a even better experience.

It's the best vertical taps plugin I had used.
I was use Microsoft Edge browser before, It has a good vertical web tab function but this one is more more powerful. It is more easy to use than Microsoft Edge's vertical tabs function, and have more good features to use than Microsoft Edge's vertical tabs function.
這是我用過最好的垂直網頁外掛。
我之前用的瀏覽器是Microsoft Edge，它雖然也有垂直網頁的功能，但是它做得並不是太好，在同時操作多個網頁時常常會有不少問題，但是這個外掛程式不僅沒有 Microsoft Edge 上述的問題，使用體驗也比 Microsoft Edge 好上不少，甚至功能還更多。

I installed it on the advise of a friend and the tree suddenly started flickering! I disabled Tree and other common extensions and it stopped. I put all of them back on and it has not been flickering. I am not sure what caused it.

请给它增加一个快速打开关闭侧栏的快捷键，谢谢。

j'adore le concept en arborescence, car ma pensée intuitive fonctionne de cette manière. par contre ce serait tellement bien de pouvoir choisir des couleurs pour s'y repérer comme dans edge. Je vais pas utiliser un navigateur microsoft pour ça, mais j'en connais certains qui ce sont fourvoyé juste pour leur super fonctionnalité d'organisation des onglet lateraux. en tout cas merci pour cette appli qui est dejà top!

I literally swapped to firefox for this extension...