The 'Select Prev on Delete' extension is no longer compatible with Thunderbird.
Request that under the Reading & Display section of Settings, add an option to open either previous or next email when selected email is deleted in the active view window. That will provide quick review of emails from the open display window. Currently when an email is deleted the display window closes, and the next email must be selected from the email account list to open the display window.
With 'Select Prev on Delete' extension, the display window closed on delete, but it did highlight the next previous mail to select.
Request this option be added to the next Thunderbird update.