Rated 5 out of 5 stars

Please make this work for latest Thunderbird. (68+) I am running an old version until this can be updated. I also added my comment to this being standard in Thunderbird on Bugzilla forum.

This is not a case of making a tab in Thunderbird, but moving the tab from the taskbar to where it should be, in Thunderbird's tab bar.

5 stars when it works!