The @links directive adds links to a page as though they were children of that page. By default the page for a directory (source file index.md if present) has as children any sub-directories or other .md pages in that directory.
So for example the Cruises page has:
@links 2007/Norway 2007 Norway 2009/eastern_med 2009 Eastern Med 2011/black_watch 2011 Baltics 2012/azores_cruise 2012 Azores 2013/rhine_cruise 2013 Rhine 2014/Azura 2014 Western Med 2015/Eclipse 2015 Norway and Eclipse 2016/Arcadia 2016 Western Med 2017/Baltics 2017 Baltics 2018/Columbus 2018 British Isles 2019/Iceland 2019 Iceland
The format for the link is a page reference followed by one or more tabs then a link title. The processing of the source files tries to be fairly smart about references to other pages (this applies to links in @markdown sections too). So providing the reference is unambiguous it should work.