@User, after our conversation I did a quick check to see what I was thinking of when I mentioned Foam's backlink meta-data in document. They are using reference links (https://spec.commonmark.org/0.29/#reference-link), which allow one to define a link for a particular block. This doesn't make sense wrt our conversation about Frontmatter, but it DOES pose an interesting idea about Github's rendering of links. e.g.

[[this-wouldnt-normally-link]]

[this-wouldnt-normally-link]: this-wouldnt-normally-link.md

The second line is ignored by renderers. I wonder if these might be added by a build flag for those that want to "publish" to a github repo and have it be navigable there.