Do you like to keep your horizontal toolbar free of clutter, but still want quick access to print preview, sync, downloads, and other options? Try using a simple vertical toolbar.
The Firefox extension is called Vertical Toolbar, and you can get it here.
The toolbar displays on the left edge of the browser by default, but can be moved to the right edge as well. Right-clicking on either the horizontal or vertical toolbars brings up more options, including "Vertical Toolbar Options."
To add or remove Firefox buttons, click on the "Customize" button.
Now you can drag and drop items from the selection box over to the vertical toolbar.
That's it. If you want more functionality than what's available in the Vertical Toolbar, try the All-in-One Sidebar Firefox extension instead.