Hello,
Thank you for contacting the support, and sorry for any inconvenience that might have been caused due to that.
Unfortunately, due to the way we are creating the sitemaps, which is dynamic, there are no physical HTML/XML sitemap files that you can edit.
Rank Math is only able to generate the sitemaps from the standard post/pages structure or CPT, you would need to create some custom sitemap either from a plugin or via our filter in this separate thread: https://support.rankmath.com/ticket/adding-extra-sitemap_own-xml-to-sitemap_index-html/
Hope that helps you with your situation.
Looking forward to helping you.
Hello,
Since we did not hear back from you for 15 days, we are assuming that you found the solution. We are closing this support ticket.
If you still need assistance or any other help, please feel free to open a new support ticket, and we will be more than happy to assist.
Thank you.
