[Question] How can I add custom XML tags to my API documentation

I see that somehow the same issue was resolved here:
https://github.com/dotnet/docfx/issues/3984

However I don't see anything about a TripleSlashCommentModel, which is mentioned in the solution for that issue, in the current codebase.

Is the answer to that issue still relevant here and if so can someone please expand as I don't understand.
Is there a new way of doing this?

Thanks,
Seth.