So I can associate an existing thread to a new event?To automatically create an associated event thread, play around with ACP->Calendar->Add category (or select one made)->Assign the forum you want the automatically generated thread under "Automatically create thread in forum" and even add a prefix (if that node allows for one you want) with "Automatically created thread prefix".
As an example, I automatically create in "Events Discussion" with the prefix "DISCUSS". If someone creates a thread elsewhere discussing the matter, I'll merge it into that thread as it's event-specific.
You could always soft/hard delete the automated discussion thread and use the drop-down "..." -> "Change discussion thread" to whatever discussion you want to take place.
Though, I would suggest merging the two so that the automated one links to the event while the discussion can carry on.
update `xf_nf_calendar_event` set `thread_id` = 9715 where event_id = 141;