For now, I am working around this by unsubscribing from the folder and then resubscribing to it. This removes that folder from the recents list.

Your workaround may be quicker.

You could try this which removes all folders from View > Folders >Recent

In Thunderbird:

• Help > More Troubleshooting Information
• Under 'Application Basics' - hald way down - click on 'Show Folder' button

A new window opens showing your Profile folders.

• Close Thunderbird now - this is important.
• locate and delete the panacea.dat file.
• Close the window.
• Restart Thunderbird.

A new panacea.dat file will be auto produced. If you then recheck : View > Folders >Recent it should only show any folder you had opened since restarting Thunderbird.

Unfortunately, panacea.dat doesn’t seem to exist any more (at least not in v102 beta on Windows). :(

Unfortunately, panacea.dat doesn’t seem to exist any more (at least not in v102 beta on Windows). :(

I've been doing some digging and discovered that the 'panacea.dat' file has recently had a name and format change, which does not effect the 91* versions but will effect your beta version. It is now called folderCache.json and it can be deleted. If it is deleted it will get recreated on restart.