No auto-completion for collection-tags accross libraries

Adding movies to an existing movie-collection works with auto-completion but if I want to add a series to an existing (movie-) collection there is no auto-completion. Haven’t tried it for the music library as I have none. In the end it all shows up in the same collection if typed correctly, so that at least works.
Is this behaviour intended?

Not entirely. Collections are still per-library, so the names of collections from other libraries won’t show up. This may get changed later.