I want to allow for MP4 videos to be selected with my media picker property editor. Under configuration Accepted types I only have an option for File, Folder and Image - How do I add the option to also get MP4 files, or would this form part of "File"?

when you add an upload field to a document type you can limit the extensions allowed

I've started adding multiple media types for different video sources (i.e. media library, youtube, vimeo, etc) so then your doc type only needs 1 property to select either one of these, rather than it being polluted with multiple fields to accommodate for all potential associated fields of these different providers. Super useful