GNOME Shell Extensions have done more than any other set of features to make GNOME 3 usable. Nearly 270 in number, they provide a degree of customization that was missing in the first GNOME 3 releases. In fact, if you choose, you can use the extensions to go far beyond Classic GNOME and re-create almost exactly the look and feel of GNOME 2 while taking advantage of the latest GNOME 3 code.
The GNOME Shell Extensions site is more than a listing of options. It is also an interface for enabling and disabling extensions. To download and install an extension, go to its page and toggle on the switch in the upper left corner. In most cases, the extension is enabled without any need to reboot or to restart the X server. To disable an extension, toggle off the same switch.
If you forget which extensions you have installed—something that is easy to do—click Installed extensions in the main menu for a complete list, each with its toggle switch.
Many of the extensions are marked as beta, but most of these install without difficulty. The few that fail to work can be toggled off without crashing your desktop. The only ones you might want to avoid altogether are the handful marked as obsolete or unmaintained. You can further minimize your chances of problems by setting the list so that only the extensions compatible with the current release display.
Few features could be simpler. If you are trying to re-create GNOME 2, you can follow these steps, focusing on choosing between the available alternatives rather than the mechanism you are using to transform your desktop.
Alternate Tab is one of the extensions officially supported in Classic GNOME, so in a recent release, it may already be enabled. If it is not, toggling it on will let you cycle through open windows by repeatedly pressing Alt+Tab.
Next, if you want icons on your desktop, enable Desktop Icon Switch. This extension adds a Desktop Icon option in the user menu on the far right of the panel. When the option is toggled on, you can right-click on the desktop to add a new folder or document.
Unfortunately, the extension does not add application icons to the context menu, but you used the file manager to add a copy or softlink of an application to the Desktop or its folders (Hint: many will be in /usr/bin).
Another popular choice is Window Buttons. Once this extension is enabled, instead of using keyboard shortcuts, you will be able to minimize and maximize windows using the traditional title bar buttons. Windows opened before you enable Window Buttons will not have the icons until you close and re-open them.
Many distributions defaulted to a top and bottom panel in GNOME 2. The Frippery Bottom Panel adds a bottom panel with a taskbar and a virtual workspace switcher, adding several GNOME 2 features with one extension. However, it requires the installation of Frippery Static Workspaces to display more than the default two workspaces.
GNOME 3 replaces the menu with the Activities link to the overview mode, which includes tools for searching for applications and launching them. For those who prefer a single screen for their desktop, the extension site includes several replacement menus:
Except for the Applications Menu, each of these extensions replaces the Activities link to the overview with its own menu. However, if you add a few more extensions (see next page), you can easily ignore the overview altogether.