Did you know that you can drag-and-drop toolbar functions to your Mozilla Thunderbird toolbar?
Well, you can!
Just right-click on the toolbar and select Customize.
The resulting windows contains a host of different functions you can just drag over to the toolbar as you see fit! You can also take existing icons away simply by dragging them back into this box or change how the icons are displayed, “Icons and Text, just Icons, etc.”.
Customization! I love it!