so,my confusion is,are you saying Opencpn can't use the internal links when they DO exist or are you asking how to write the internal links
Because in html,I think you would need to write them...SeaMonkey Browser is a great one for this.You can open and edit existing html page.
If I get you right,you want to do as they do online...
When I open a page stored on my hdd,it looks like this:
that page has it's own links that take you down the page(not to a different page) as in this:
the #what and the #dupes are the thing...
using Firefox menu I find View/page/source and it looks like this...
a bunch of stuff ahead of it and after of course...
<li><a href="tabtrick.html#how">How file name completion works</a></li> <li><a href="tabtrick.html#dupes">Files starting with same letters</a></li> <li><a href="tabtrick.html#what">What can be completed</a></li> <li><a href="tabtrick.html#ref">What next?</a></li>
the user sees"What can be completed" not "what" and so on
Sorry I don't have a boaty example ...anyways it's an html coding question you are asking,I think
Unless you know all this.sorry.