Thunderbird's toolbars provide easy access to common features. This article explains how you can customize toolbars to make Thunderbird work the way you do.
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.
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.
See these toolbar troubleshooting articles: