Well, technically it is covered in SEMOS (section 5.1.2), as this situation is no different than a link to text.
If something says “see p. 123” and p. 123 is referring to text, then we put an id on the (first) paragraph being referred to and link to that id. Unlike an endnote, this kind of reference is a one-way link.
If it’s “see note on p.123”, then we don’t have to create an id, because one already exists, i.e. the endnote id. But like the above, it's a one-way link.
So if endnote 100 is referring to text, which turns out to be in chapter 12 paragraph 5, then we put an id on paragraph 5, and the link in endnote 100 would be
See discussion <a href=“chapter-12.#chapter-12-p-5>here</a>.
If endnote 100 is referring to endnote 53, then the link in endnote 100 would be
See discussion <a href=“endnotes.xhtml#note-53”>here</a>.
In both cases, getting back is up to the ereader. Most ereaders (that I’ve used, anyway) keep track of where you came when you jump somewhere and offer a way to get back.