Wikipedia:Legacy toolbar

In June 2017, the maintainers of MediaWiki announced that the legacy 2006 toolbar would be retired. The removal from the software was delayed, and eventually re-announced in October 2018 and made effective in November. Since a number of editors prefer the old toolbar interface to the new 2010 version, the 2006 toolbar was preserved and re-implemented as a user gadget.

Installation
Installation of the base toolbar is easy: simply go to Special:Preferences and, in the Editing section of the Gadgets tab, check the box next to Enable the legacy (2006) editing toolbar and hit the Save button at the bottom. As the description says, this gadget is not compatible with the 2010 editing toolbar; the 2010 toolbar will override the 2006 gadget if both are enabled. Thus, one will also have to disable the 2010 toolbar by unchecking the Enable the editing toolbar option in the Editor section of the Editing tab.

Between the retirement of the official toolbar and the introduction of the gadget replacement, the toolbar was available as a user script (located at User:Writ Keeper/Scripts/legacyToolbar.js). It is recommended to uninstall the user script version (by removing the associated  line from one's common.js page or specific skin page) and install the gadget version.

There are additional buttons that have been developed and added as gadgets on their own. Those are the refToolbar (compatible with both the 2006 and 2010 toolbars) and the "Add extra buttons" gadgets located directly underneath the legacy toolbar gadget; enable them as well to acquire the additional options. The legacy refToolbar was also available as a user script; uninstallation of the user script version and reinstallation of the gadget version as above is also recommended.