I was interested in that functionality as well, so I developed my own version of it. It can be found here and already is in nbbpm (can be installed from ACP by searching for nodebb-plugin-category-queue) It has some basic ACP (list of categories with options to queue new topics from them or not queue), and only works on new topics, not all posts (that is actually by design, as - after all - you have done the work on filtering posts already. It's just that I was looking for only sending new topics to queue)