Site Administration allows the creation of new tabs in the UI by using view mappings. Adding a tab to a view involves appending an itemViewMapping to a particular category’s itemMapping property. For example:

<update-item item-descriptor="itemMapping" id="SaImSiteDefaultCategory">
  <set-property name="viewMappings" add="true"><![CDATA[mCRSTab]]>
    </set-property>
</update-item>