On deleting an email the pane which lists all emails (?message list?, top right) is cleared and the only way to restore it that I have found is to close Thunderbird & reload. Strangely this process a) says that Thunderbird is still running; b) creates a new extra drafts folder (Drafts-1) with the same content as the original Drafts folder; and c) creates a new folder named Drafts.msf-X.compact-backup. I have tried reverting to an old version; and have installed the latest (136.0.1) to no avail. This occurred a week or so ago if my memory is correct.