Most toolbars can be shown or hidden depending on your needs.
To show or hide a toolbar, right-clickcontrol-click on an empty section of the Tab Strip at the top and check or uncheck it in the pop-up menu.
Menu Bar: This toolbar at the top of the Thunderbird window contains the browser menus (File, Edit, Help, etc.). On Windows Vista and later versions, the Menu Bar is hidden by default, and its features are contained in the Thunderbird Menu button (the button with three horizontal stripes on the top right). If the Menu Bar is hidden, you can temporarily show it by pressing the Alt key.
Menu Bar: This toolbar at the top of the Thunderbird window contains the Thunderbird menus (File, Edit, Help, etc.).
Menu Bar: This toolbar at the top of the Thunderbird window contains the Thunderbird menus (File, Edit, Help, etc.) and you can't hide it on the Mac.
Mail Toolbar: This toolbar (which is underneath the Menu Bar) contains mail related buttons and menus such as Get Mail, Write, Chat, Tag, Quick Filter, etc.
Tab Strip: This is where your tabs such as the tabs for your inbox and for Thunderbird Add-ons are displayed. You can't hide it.
How do I customize or rearrange toolbar items?
Right clickControl click an empty section of the Tab Strip and select Customize....
The Customize Toolbar window opens.
Change the toolbar items as necessary.
To add an item, drag it from the Customize Toolbar window onto the toolbar where you want it to appear.
To remove an item, drag it to the Customize Toolbar window.
To rearrange an item, drag it to the spot where you want it.
When finished, click Done.
Try it out: Experiment with different arrangements. You can always restore the default toolbar settings by clicking Restore Default Set in the Customize Toolbar window.