This looks like it'll be a good add on when/if tabs can remain open and don't need to be reloaded when switching between tab groups. I, however won't be using this until then.

UPDATE: 03/11/2019
Thank you so much for adding group-sorting options and fast switching! I have, at last, fully migrated to this add-on from Firefox Multi-Account Containers for group sorting alone. Got tired of waiting years for something so simple–yet you implemented it right away! Love the customization options for groups–colors, icons, etc. And it works great with Tab Suspender to save memory. Upped to five stars!

Latest Suggestions:
• I love how one group is shown at a time. On the other hand, it would be nifty to have the option to show more than one group at a time.
• It would be great if there were symbol options for the group-switching icon similar to Firefox Containers to easily identify the group selected.
• When moving a tab to another group, one must first click within the web page of the tab being moved. It would be nice if it would work when just clicking the tab.

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ORIGINAL REVIEW:
Finally, a comparable replacement for Tab Groups! It appears to make due without the tab-hiding API by closing tabs (rather than hiding them) when switching groups. This is what I have been waiting for.

Suggestions / Requests
• Please add a way to reorder and sort tab groups by name in group list.
• Please show the name of the currently-selected group next to the add-on icon.

It's better than nothing, but still a far cry from the original Tab Groups. To prevent repetition, I would like to refer to the comment of J-Dude and hope you will indeed improve this extension, so that it will really be worth using it.
It's a start, but you will need to keep up the good work to increase your number of stars.

Сегодня тестил это расширение. Переключился на новую группу, переключился обратно - а оно заново грузит все 100 вкладок. Я закрыл, подумав, что всё загрузится по клику в отдельности, но получил пустые страницы. Хорошо ещё, что все они сохранились в истории, но увы, вперемешку.
Тут увидел, что в расширении можно импортировать настройки из старого Tab Groups. Но я не могу найти файл настроек в поиске. Как это сделать? Хорошо бы инструкцию для импорта.

Works as expected, only thing I would like to see as mentioned in other reviews, is the option that pages do not have to reload until clicked, or that they are cached and don't have to reload.

This is great, just what I needed as I was lost without my tab groups an the import worked well. I would like to see the option to reorder the groups in the drop down menu, either alphabetically or drag and drop so that my most frequently used groups are near the top. Also to have the ability to open a group in a new window.

Add-on works nicely. I also imported from "tab groups" backup and it worked.
Thanks!

There are 3 things I would be happy if you added:

1. A simple way to move tabs between groups.
2. Don't load all tabs when opening a group. Only open tab when selected.
3. Manage tab groups and tabs in a overview window.

Edit:
These things exist now. Great add-on!
Thanks!

I look forward to when this can handle my everyday use as tab groups did. Right now it does not do what I need. I cannot easily move tabs between groups, cannot name my groups, and when I select another group I have to wait for all the tabs to reload which really slows things down. Also, if I have music going in a tab and I switch groups, the music stops. So right now it's a no-go for me, but I'm hopeful for the future of this Add-on cause I'm really missing tab groups since the Firefox Update.

This is what I wanted but it will great if you change the behavior to open only activated tab instead of reopen all when users select a group.

Works like a charm, author keeps improving it.
Not sure if possible with the new API, experience would be cleaner if it didn't reload tabs on switching (but kept them in memory)

If I move a tab between two windows, the tab didn't auto add in group, until I press create a new tab(ctrl+T).

Спасибо большое за плагин! Отличное начало. Ваша работа дает надежду всему сообществу :-)
Возможно ли в будущем избежать перезагрузки вкладок при смене группы? Или есть техничекие препятствия со стороны новой платформы FF?

Спасибо за дополнение, отлично работает в FF57, не совсем понятно только почему оно не вначале рейтинга, наткнулся случайно. Из пожеланий, не мешало бы импорт добавить из старого аддона Tab Groups quicksaver-a и будет вообще вещь!!

This morning I was distressed to find my version of Firefox had automatically updated and my tab groups were gone. Noooo! However, I'm pleased to have found this new replacement. I've been using it about 10 minutes so far ;-) My only suggestions at this point would be the option to name the groups, and to be able to drag and drop between groups. Other than that, THANK YOU for creating this. I don't want to go back to the stone ages with all my tabs open at the top.
Have a great day! :)

Very usefull ! Miss shortcuts to go to the next/previous group hope you’ll add it some day !
Thanks

Very Useful and promising addon.