I've got this issue where I built pretty nice mogrt from Premiere Pro to use on Rush (because Ae's engine, etc), I even used them on a sequence (yeah, rejoy).
Then, I shot a couple of minutes interview to put my motions to a test.
And I got STUCK.

1. adding a new title, there was moments I could not get a CCLib style, only the ones built in.

2. I NEVER know where I shall click in the app to get those other CC styles : Titles > more titles > magnifier >>> look inside > All/favorites. Sometimes, I get no CClib down there. And sometimes, I don't even get the All/Favorites dropdown at all. And sometimes, I'll wait long enough and the mogrt/titles will appear. There's no visual feedback for loading, so maybe I just didn't wait long enough before.

3. There's also the favorites. In a project, I'll always go to those three (intro, question, ending). So I starred them. Which might be interesting if the favorites/stars where displayed for a folder or for all my mogrts (built in, from all cc libs)…

4. Side joke, the ordering of CC libs sucks :
   on the desktop, we have the 10 most recently edited libs (clever choice), then alphabetical order.
   on Rush (and other CC apps, so it might be an API issue, not on your side), it SEEMS to be the order of creation of the CC libs.
   I mean, I've been using CClibs for as long as they existed. I have dozens of them, some have close or related name (clientName - projectRef…).
   If it's not "complicate" to implement, don't hesitate to fix that :)

Voilà, so far.