Adding links to the "Related Forum Threads" section of any wiki page is easy, all that is needed is the numerical id of the thread to be added.
For example, the id of the 'Morrissey A-Z: "Alsatian Cousin"' thread is the number at the end of the URL, 147523:
Add this to the "Alsatian Cousin" wiki page by clicking on the "Edit page properties" on the left sidebar (under navigation) of the page:
On the edit page, in the RelatedForumThreads add the thread id 147523 and save the page (warnings for first time adding RelatedForumThreads can be ignored). Multiple links can be added multiple thread id's, separated by comma. An example of a page with multiple Related Forum Threads is https://www.morrissey-solo.com/wiki/Suedehead_(single).