https://github.com/barisusakli/nodebb-plugin-topic-noindex This is a plugin that does it for topics.
There is no built in way to do it in core. So to do it for categories you would have to fork and extend the above plugin.
I am using recent topics page as my home page and I want certain topics to stick at the top e.g. a welcome and an introduction topic. Any ideas on how to do so ?
Anyone else has some idea on how this could be achieved ?