As part of the work being planned by the Thunderbird UX Team, a few weeks back we discussed in a past UX meeting about what to tackle next in Thunderbird UX wise. Based on the Usability Study we published past summer ( https://ura.design/projects/thunderbird ) we decided to have a go at redesigning the Preferences (Options in Windows) view to be aligned with how Firefox displays its counterpart.
You can check out the details at the bug as well: https://bugzilla.mozilla.org/show_bug.cgi?id=1498332
We currently have also a prototype ready of the proposed restructure: https://www.figma.com/proto/DAIuhXdQ0G9AExbKLCQZ1HSE/Settings?node-id=12%3A560&viewport=288%2C524%2C0.426706&scaling=min-zoom
Very soon we will write a short Design Study on this work to explain the motivations behind design decisions we took, followed by User Testing which will surface any potential problems users might have and compare current and proposed designs.
Let us know if you want to get involved in designing and shipping this!