There is currently no way to change or add URLs to a MarkUp. You will need to create a new MarkUp for URLs that are not linked to your site.
MarkUp Top Tip: If you have a lot of pages that cannot be accessed from your site, create a temporary page that contains links to all the inaccessible pages and load it in a new MarkUp. You can delete this page once you’re done with the project.
Need further assistance? Feel free to reach out to our support team!