Tags not retaining styles on import: XML

I may be missing something obvious, but I cannot find a single answer online for this.

I have a large list of tags mapped to the correct style required, and have saved the XML. When I create a new document, I can obviously load the Paragraph/Character styles from a previous document, but when I load the XML file for the tags, they do not retain any mapping to styles, even if the styles are preloaded into the new document beforehand.

Is this not something that is supported? Or is there somewhere in preferences, or an answer that can allow this? I'm working with a team of people, so being able to load tags with existing mapping into a pre-created document is sorta vital. Otherwise we'd always have to start with a template document and amend the setup/size etc each time, which I'd really like to avoid.

[Title edited by moderator to include "XML"]