I have been out-of-the-loop and thus not aware of the Channels Collections beta that got rolled out officially today but after playing with this for an hour on the server web page and on my Nvidia Shield, this enhancement is either one of the most unintuitive implementations I've ever come across or it is super buggy on the Android client or possibly both.
I've been messing with settings and cannot figure out rhyme or reason as to why things show up or disappear and I can't seem to get consistent behavior either.
At first in the On Now screen all I had was the normal categories. I finally figured out how to get one of my custom collections to show but then all but "All" and "Favorites" and my custom one would show. I guess that's by design, but why would I want to create a collection and then lose many of the custom categories already on that screen is beyond me. There should be an option on which ones to keep, rather than me having to create them manually.
After further changes, all of the sudden the on now completely disappeared and I could not get it back until I restarted the app, but now I have zero categories in the on now and no matter what I do they will not come back.