Thanks to Robert for answer to that, then there are other options with the admin wrench to unlist, close, archive, or delete a whole topic thread. Unlist means it won’t show up on site topic list, but anyone who has been commenting will be able to continue to talk there unless you close the topic, put it in slow mode, or moderate anyone who isn’t abiding by the community guidelines.
(Note: community members at trust tier #3 can also re-categorize some topics to different categories)