TLDR: Converting a thread to an article should also move the discussion thread to the forum set in "Automatically create thread in forum".
Longer:
If you use the "Convert thread to article" option AND the article category you are converting the thread into has a value for "Automatically create thread in forum" - then I would expect the discussion thread to be moved into that forum after conversion has taken place.
I did wonder if this was intentional - however I believe it's a bug - as if once the thread has been converted to an article and you then move the article to a different AMS category (which also has "Automatically create thread in forum") - then the discussion thread will also be moved to the aforementioned forum.
This also affects Showcase.
Longer:
If you use the "Convert thread to article" option AND the article category you are converting the thread into has a value for "Automatically create thread in forum" - then I would expect the discussion thread to be moved into that forum after conversion has taken place.
I did wonder if this was intentional - however I believe it's a bug - as if once the thread has been converted to an article and you then move the article to a different AMS category (which also has "Automatically create thread in forum") - then the discussion thread will also be moved to the aforementioned forum.
This also affects Showcase.