[bhasi]

I don't see anyone mentioning Betterbird here. I use that instead of Thunderbird. But it really baffles me that even in Betterbird, the ability to star an email exist but not a way to show all the starred emails.

[boisterousness]

In Thunderbird's message list, you can bring all the starred emails to the top by sorting on the star column. Just click on the column header.

Also, in the Quick Filter, you can click the star button to "Show only starred messages".