Key in DELETE UNUSED ELEMENTTEMPLATES to delete ALL unused element templates.
Key in DELETE UNUSED ELEMENTTEMPLATES <TemplateName> to delete a specific unused element template.
Deletes element templates that are not associated to any graphic element in the open DGN or DGNLib file. If the open DGN or DGNLib file is specified in the MS_DGNLIBLIST
configuration variable then no element templates will be deleted.