It would be very nice if, in a Thunderbird installation with many email mailboxes including many IMAP folders, it were possible to perform a quick filter using this list for the Thunderbird GUI object, this "tree view" with the email mailboxes and email folders per mailbox.
1. Focus on the left navigation bar.
2. Press Ctrl+F to open a small text box with autocomplete. As you type, the view will reduce to the selected mailboxes.