Actually it might still ‘exist’ but no longer work.
Have you seen the Favorites - select your favorite categories?
You can choose which categories to include in ‘favourites’ and view them all together with one click. That click will exclude all topics from categories not included in your favourites list.
Would that behaviour fit your requirement?
It is broken, but I did offer the community my services to fix it if it was sponsored. I may already have a co-sponsor to share the cost with.