When showing only movies, the collection is also showing.
In the picture the movie 300 and collection is showing, even if only movie (film) is on.
here you go…
support articles are your friend 
this feature actually already exists since end of last year (in beta).
when editing the library you can define if/how collections should show “inline” with your movies (inline collections → disabled, hide items which are in a collection, show collections and their items).
Since one of the very latest releases you can also configure exceptions for each individual collection.
