Giving names to the forums, for fun:
Parent forum = Peter
Children, sub-forums = siblings Charlie, Doris, Ethel, Fred and Graham.
Question: can Graham become a child (not a sibling) of Charlie?
Expressed another way: can Graham become a grand-child of Peter?
Expressed another way: can a collection of threads (a container, if you like) be moved?
The third expression of that one question seems to be answered under point 2 of
<
http://n2.nabble.com/help/Answer.jtp?id=43>.
I see also <
http://n2.nabble.com/Suggestion%3A-Advanced-forum-editing-td220913.html> and as my guide I have <
http://n2.nabble.com/help/Answer.jtp?id=24> but to begin with, I'm experimenting to see whether a limited hierarchy of forums — one that is reasonable — can be changed without too much difficulty if, at a later date, there arises a genuine need to do so.
I don't imagine great-grandchildren but a move from sibling to child, or vice versa, seems a reasonable use case.
TIA for any advice
Graham