Collection shows all the movies I own.
Watchlist shows all the movies I want to watch.
What about when I sit down to pick a movie and want to browse all the movies I own that I haven't watched yet?
Awesome, thanks for working on this, Kevin!
This can be accomplished by adding a checkbox in Watchlist says "show only movies in my collection" or simply adding collection icon (check mark) on all the movies I own in Watchlist.
This is kind of like the inverse of the Wishlist.
Wishlist is for movies on your Watchlist that are NOT in your Collection.
This is for movies on your Watchlist that ARE in your Collection.
Maybe you could call this Watch Next or something like that, and the icon could just be the icons for Watchlist + Collection.