I have noticed something about collections that cross library types:
Let’s say that you have 5 different Brady Bunch TV shows (yes, there were 6 different ones but one is almost impossible to find, but I digress) and so you create a “Brady Bunch” collection in that library and they all group together. Yippee!
They you find that you also have the 4 (yes, four!) Brady Bunch movies and so you create a collection for them and call it “Brady Bunch” also. They show together and they show within each other also. So, within the Movies collection, there is a sub section for TV Shows in the Brady Bunch collection. So far so good!
Now you find your two Brady Bunch albums (one regular and one Christmas music). So, you create a collection tag in each of those libraries that is also called Brady Bunch. Now, when you look at the Movies library and see the Brady Bunch Collection, it shows the 4 movies, the 5 TV shows and one album from the Music library and one from the Christmas Music library. All of this is great. It works the same way when you look at the collection from within the TV Library.
However, if you look at the Brady Bunch Album in the Music libraries, there is no mention of the associated libraries with tied output. No other collections are shown. I’m sure “someone” has a good reason for this but I don’t think it will hold up. Since we can see all of the associated content one way, we should be able to find it another way.