I have characters that have a value "author" which is tied to an author post.
Then I have a book post type, which is tied to an author through a post field. It also has a character field which is a post select field as well. I would like to limit that character dropdown showing on the books page to only those characters that are assigned to the same author as the current book. Is that possible? I tried everything possible I could think of in the Query values in the advanced tab, but couldn't get anything to filter it.