Opens the Add-ons window to perform tasks on your installed Extensions, Themes, Plug-ins and Language packs.
The Add-on's window allows the installation and management of all your extensions and themes. If you need an update, change a setting, swap themes or enable/disable an add-on the Add-ons' window is the place to go. Being able to access this quickly is a necessity for anyone that uses even a handful of add-ons.
The button also contains a drop down menu that allows you to install add-ons, open the add-ons window to the extension or themes tab, or set which websites can install addons.
This button is a legacy add-on, and can not be ported to Firefox 57+.