Sorting seems to be non-effective with extensions such as the ones below:

Tab Sidebar
https://addons.mozilla.org/addon/tab-sidebar-we/

Vertical Tabs Reloaded
https://addons.mozilla.org/addon/vertical-tabs-reloaded/

Visual Tabs
https://addons.mozilla.org/addon/visualtab/

Do those extensions lack what's required? (Are you aware of an alternative vertical tabs extension that might work with Tabs Manager?)

Thank you

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Past reviews, in the Wayback Machine:

https://web.archive.org/web/20200125171132/https://addons.mozilla.org/en-US/firefox/addon/duplicated-tabs-manager/reviews/923272/

https://web.archive.org/web/20200125171003/https://addons.mozilla.org/en-GB/firefox/addon/duplicated-tabs-manager/reviews/933235/

https://web.archive.org/web/20200125170802/https://addons.mozilla.org/en-GB/firefox/addon/duplicated-tabs-manager/reviews/950983/