Thunderbird version 102 has a Spaces Toolbar.
https://blog.thunderbird.net/2022/09/thunderbird-tip-customize-colors-in-the-spaces-toolbar/

Can a ThirdStats icon please be added to the Thunderbird Spaces Toolbar?

Perhaps code pointers from the CardBook add-on can help as a CardBook icon shows in the Spaces Toolbar.
https://addons.thunderbird.net/thunderbird/addon/cardbook/
https://gitlab.com/CardBook/CardBook/

What do you think?

Thank you