This has been fixed for 1.6: https://lists.webarch.co.uk/pipermail/mkdoc-commit/2005-August/000915.html
Actually, the bug was that hidden documents should be visible to editors, not that they should be visible to hidden documents. This second patch fixed this for 1.6: https://lists.webarch.co.uk/pipermail/mkdoc-commit/2005-August/000946.html
Hidden docs should have hyperlinks automatically generated for hidden child documents, see the 1.6 and 1.8 hidden docs don't link to other hidden docs thread.
The code that generates the links to showable documents is this in flo/Editor.pm:
# plus we want to hyperlink all the children foreach my $child ($document->children_showable) { push @links, { class => "mkdoc-name-". $child->name, href => $child->uri, desc => $child->description, expr => $child->title, lang => $child->lang, } }
I guess it needs wrapping in an if that does, if this is a hidden document then link to all child documents irrespective oftheir showable status else only link to showable documents.
This will be a bit more complicated for 1.8 because there shouldn't be automatic links to versioned documents…