You may already know that there is no status bar from Firefox 4  release onwards, Mozilla moved some status bar features to navigation bar, Add-on Bar is not the status bar but it has been made available for the placement of add-ons icons, this is not visible by default you can show/hide it with Ctrl + / shortcut or use the option available from the Firefox menu button.

What’s the need for A Better Firefox Add-on Bar?

Some add-ons does add their icons to add-on Bar for quick, over the time bottom right-corner of Add-on Bar will be flooded with icons which nobody likes. A Better Firefox Add-on Bar is Firefox extension tweaks default add-on bar and also hides add-on icons, they’re only shown in neatly organized manner whenever you hover your mouse pointer over bottom area on right side of the window.