If there was one thing I could say about the new Firefox 4 layout and design, it would be that minimal is the new black. It seems that moving forward we are going to get less and less user interface. So, to help follow that eventual trend in design – let us go ahead and shrink the new Add-on Bar down some with Barlesque.
Barlesque is a Firefox 4+ extension that will do the job. Once installed, make sure you have the Add-on Bar turned on (by going to View > Toolbars > Add-on Bar under the Firefox button). You should then see that the Add-on Bar is no longer across the bottom of the window. It is now collapsed into the corner of the screen. This way the add-on bar will only take up a fraction of your overall screen real estate.
You have the option to place the icons from the Add-on Bar either to the bottom left or bottom right parts of the screen too.
You can pick up Barlesque from the Mozilla Add-ons website.