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.
We are relaunching our forums with just two main sections. I am struggling to delete older forums... here you can see where I took the details off one and disabled it, yet it is still showing on my homepage... any ideas?
At the same time - one I really need to be there has disappeared! I just want: QTLS, Practice Forum and SET Community.
@JKF80 what version of NodeBB? Disabling the category should remove it from that page. Are there any errors?