There's various old threads regarding this and Tags:
I propose making Metadata fields such as Genres, People, Studios, Tags (and any other field this might make sense for) Autocomplete-capable so that we can start typing and see a list of existing options to choose from. This will help a lot with making sure we are staying consistent and not accidentally adding a new variation on an existing value.
Thanks for considering my request!
PS - If this is something you might like to see implemented, be sure to "Like" this top/first post (as well as any subsequent posts in this thread that highlight particular aspects of what you are interested in) -- "Liking" the top/first post helps the Devs to know how much interest there is in a given Feature Request.