Yeah so essentially what you want is to do is create an equals template helper, here are a couple resources from the past:
And the benchpress docs
Like discourse where all the posts can be displayed in one page and also can be filtered by their category? I feel that model makes category more like a tag and allows people to see everything at once.
Is there technical issue why this cannot be achieved? Maybe it can be a theme idea?
I really like nodebb as a fast and modern forum technical wise, but also enjoy the UI philosophy behind discourse..