Before gatein 3.5.0.Final, you can't overwrite templates in portlet's war, to change the template in the navigation (UIStartToolbar in you case) , you'll need to overwrite this file https://github.com/gatein/gatein-portal/blob/3.5.0.Final/web/portal/src/main/webapp/WEB-INF/conf/portal/portal/sharedlayout.xml (use extension machanism --> put this file in your extension war) and replace the StarToolbar portlet by your portlet
With gatein 3.5.0.Final, we provide a way that give user more control on how the application template should be resolved, you can write a PortletApplicationFactory (declare by using ServiceLoader) in your extension, this factory will return a PortletApplication object which is in charged of resolving the template by providing a PortletResourceResolver --> in your resolver, you can refer to the Portal's resolver like this:
PortalRequestContext context = Util.getPortalRequestContext();
--> portal's resolver will allow you to overwrite the portlet's template (by put that template in extension project)
Here is the related commit https://github.com/gatein/gatein-portal/commit/c6725ca
@Phuong: Timothy mentionned that 'without having to modify the main container files"
@Timothy: If i remember well, the drop-down list is part of Star... portlet, so you could adjust its access permision