I have two landing pages. I have tried adding them to the Additional Starting URLS list in the Advanced section. They show up in the generator.conf file are never added to the sitemap. I finally figured out the issue. It needs the whole url not just the page name. There may be a reason for it, but you should add a note to that field so we know. Otherwise, it is confusing since the other fields do not require they entire url (instead of sad.php - it requires [external links are visible to admins only]). Then it works just great.