Thunderird update 115, Supernova, adds a bar above the start menu that includes a lot of wasted space and a search box in the middle. Whilst the bar can be customised, unfortunately Mozilla developers have chosen not to add an option to remove it through settings.

To remove the bar:

1. Tools -> Settings -> scroll to the bottom for Config Editor…
2. Search for: toolkit.legacyUserProfileCustomizations.stylesheets,
   and set to true
3. In file explorer open %appdata%\Thunderbird\Profiles\<your-profile>
4. Create a directory called “chrome“
5. Within the chrome directory create a text file: userChrome.css
6. Add the following lines to the CSS file and then restart Thunderbird:

unified-toolbar { display: none !important; }
#toolbar-menubar { height: 28px; }

These lines hide the unified toolbar and increase the menu bar size.

These frustrating changes continue to come from Mozilla, despite recent promises that they wouldn’t impose jarring changes on users. If you too are frustrated by these types of changes consider investing in a product like Mailbird – www.getmailbird.com.