This customization adds two new items, equivalent to the above tool bar buttons, to the stock DocBook menu. See configuration element menu.

  <menu label="_DocBook" insert="Move _Up">
    <item label="Open in Default _Viewer" 
          icon="icons/openInDefaultViewer.gif" 
          command="docb.openInDefaultViewer" />
    <item label="Edi_t Document" 
          icon="icons/editDocument.gif"
          command="docb.editDocument" />
    <separator />
  </menu>

Note the insert attribute in the menu element which is used to insert the two new items and a separator before the "Move _Up" item found in the stock DocBook menu.

The insert child element and the insert attribute are the two ways to extend existing tool bars and menus.