There are several standard widgets that come with the standard &xwp; distribution.
To add a new widget to an open &xcenter;, right-click on an empty area on the &xcenter; bar and select one of the available widgets from the "Add widget" submenu.
Note that to add an object button widget, you can simply drag any Desktop object onto an empty area of the &xcenter; bar.
See &xcenter; mouse operations for
more information.