Hi Adrian.

I'm afraid not. 

At the moment, the Sitemap gets automatically generated by the software, and it cannot be edited in any way from the software itself.

Should you wish to apply any kind of edit to it, you would have to do it manually after export, which of course means that it would get overwritten after every new export.

I believe this could prove to be an useful improvement to the software anyhow, and for this reason, I suggest you open a new Idea topic on this, so that the Staff might better keep it under check

Thank you for your feedback

Stefano