You mean autosave in Tree Tabs or external? My groups are internal in my extension, so if you close groups, you lose them. There is no way to restore. My extension has its own autosave, but loading autosaved session is horrible at the moment as Firefox does not provide a way to create tabs without loading them, most of the time browser is not responding and my extension just hangs, hence problems with rearranging tabs in correct groups... I'm preparing an update for Firefox 63, which will be out in 3 weeks, where creating unloaded tabs is possible (works already in Firefox beta). Most of the bugs related to it will be resolved thanks to this.

Closing the last tab in a group (if there are still tabs left) will not activate another group in the next update, but only if you close tabs from within the sidebar (with mouse, not by a shortcut or mouse gesture).

Can you explain what you mean?

Did you install any additional extension before it started happening? If so can you list me all of your installed extensions? Email me at Support Email that is provided here in extension's description, so I can help you out :)

EDIT: I've read your edit just now, because I didn't see it (the one line at the bottom)... Sorry for late response.
Go to Firefox Options - Advanced at the bottom - Network
Try to Clear Cached Web content and Offline Web content.
If it does not help you will have to wait for update. Sometimes cached files are still in use, so it's kinda hard to clean up everything. In next update I will provide emergency button in Tree Tabs options and load backup buttons in toolbar. In your case you probably will not be able to recover last session, but in the future when that happens again, yes. I will provide 3 backups. I'm thinking to provide save backup to hdd, but I'm not sure if I will be able to finish it for this update.


My brother had this same problem yesterday, as few other people. If options page shows up without a reason it means localstorage data got corrupted or some part of it cannot be read. Same goes for your trees. Some have just a blank white page instead of the sidebar. Looks like Firefox has some problems with retaining localstorage, it might be that some process close unexpectedly corrupting data while saving it to hdd. In my experience it happens from time to time, but it's more frequent with last few updates of Firefox.
They may be in hurry to release 57. I don't know just guessing.

You have to clean local storage to fix it, otherwise problem can come back.
https://stackoverflow.com/questions/18877643/error-in-local-storage-ns-error-file-corrupted-firefox

In a new version of my extension I will save a lot less data, but I cannot guarantee all will be perfect and I have a lot to fix to release it. Anyway it is a good idea to save your theme like you said.

Read post and my response above

Web extensions are pretty much limited for now, probably there will be some way to sync with other devices, or bookmarking options, in the future, but for sure it won't be soon. openerId is in the works by Firefox folks, it will start working as soon as it's implemented in Firefox, so be patient it will be there.
I will hide tab bar as soon as it will be available, there is an experimental API in the works as well. I have an update in the works to sync tabs on top, so ctrl+tab will work as it should.

I do my best to get all the kinks out.

Please don't disable extension, it must be enabled to retain trees. Sidebar can be closed, but extension must be enabled.
With new Firefox API, tabIds are lost after browser restart. Extension must keep track of all tabs positions all the time. This is unfortunately a limitation to all chromium based browsers and Firefox joins that trend.

Hiding tab bar is unavailable from Web extensions for now. Please join conversation at bugzilla to convince Web Extensions team to give us this possibility, here:
https://bugzilla.mozilla.org/show_bug.cgi?id=1332447

For now search for an alternative extension that just hides tabbar, for example Hide Tabbar (in this particular one, uncheck reopen tabbar when opening a new tab in options, it does the trick)

theming is another limitation, and will be for all new Firefox extensions. As new sidebar extensions are just web pages with special privileges to have access to firefox API's like tabs favicons, titles, we can activate, move them in tabs strip at the top and so on. Tabs in my extension are not real tabs with changed look, this is just a web page with generated buttons that link events with the browser. All new extension will work this way in the future. I did my best to give it at least color customization. And remember this extension is cross platform, it works in Opera/Vivaldi and now in Firefox, so I can't make colors match only one of the bunch.
Anyway you can download dark theme at (and hopefully you can share yours as well):
https://forum.vivaldi.net/topic/15332/tree-tabs

Tabs hierarchy management will improve with time as I implement more and more features, and not only me, it depends on Firefox team as well, as for example Firefox does not have "openerTabId", so new tabs opened from middle click will not append to the tree, you must set "Append orphan tabs" to "treat as active's tab child"
For this matter, you can also join conversation at:
https://bugzilla.mozilla.org/show_bug.cgi?id=1238314


Thank you for testing my extension in this early stage :)