The MongoDB storage adapter of Parse Server already has a caseInsensitive option to add a specific collation for case insensitivity to the find query, specifically it sets { locale: 'en_US', strength: 2 }.
Is that what you are looking for?
If you want to propose exposing exposing more/all of MongoDB’s native collation options, I suggest you open an issue in Parse Server and reference this thread here to make a feature request.