To benefit from autocompletion you just have to add the correct XML Namespace to the various xml files like views, portletentities configuration file or portal configuration. Use the following URLs:
Views:
http://www.gentics.com/xml/ns/portal/view
Portlet Entities Configuration:
http://www.gentics.com/xml/ns/portal/portletentities
Gentics-Portlet Descriptor:
http://www.gentics.com/gentics-portlet-app