How does org identify which table rows should be exported with header tags?
It seems rows above a horizontal line are automatically converted using
<th> tags. Is there a way of controlling this?

My specific use case is that I have a multi-row table header created in an
R code block. I do not have a way of creating a horizontal line, and
without that the header is not being recognised as the header in html
export.

Would be grateful for any pointers.

Vikas