That’s awesome and probably the thing I actually need, because then I can have the box for the sub category! 
Thanks for the link to the tag banner. Will definitely install that as well.
I need to go and test it myself to fully understand how that works.
Thank you so much for your continuous and extremely helpful replies, especially on the beginning of my journey with Discourse, which I’m loving so far. I’m glad I decided to go the self-hosted route. I was a bit afraid of all the extra work, but it’s definitely worth it!