1. Search Results:
To get better search results, I'd suggest to add a possibility to either search for people or for titles. If I'm searching for an actor (no matter if I use Western writing or the original language), I often have to scroll through the titles of numerous movies and series until I get to the actor, I want to look up.
Splitting the search up in people and titles, would make it easier to find what one's looking for.
2. An additional possibility to differentiate cast members when adding new titles:
At the moment, we can choose between Main, Support, Guest and Unknown, if we want to add cast members to a movie or series.
I think, adding 'Co-Star' to the choices would make it easier to differentiate between characters as there are leads, important characters, supporting characters and guests (especially if we have multi character drama series with more than 40, 50 or more characters).
I think, 'Supporting character' often doesn't fit or match with the characters' roles in a drama as they are actually characters, who are very important for the story and not just giving the leads a keyword, like a supporting character would most likely have to do it. And if you look at the openings or the end credits of movies or drama series, you'll find it in a similar way: Main, Co-Stars, Supporting Cast, Guests/Special Appearances.