Noindex all pages by default, sitemap not showing single pages that are index

Hi there!

We have a problem where we want to exclude all pages by default (and have made those settings already), but have the option to manually include some pages.

Now we’ve set that option in the advanced options of the page, but the page-sitemap.xml doesn’t update and show the one page we’ve selected for indexing.

Is this not possible if all pages are being excluded by default?

Thanks in advance!