Typically when you add a song to a playlist it adds it to the bottom of the playlist. However, it would be great if you can choose to automatically add it or reorder it to the top so you can play your most recently added songs first. Maybe a function to reorder playlist by, “Date Added” feature would work.
Updated on 2019-08-10
It's possible to sort playlists. On a computer you can do this by clicking any of the column titles like Title, Artist or Album. Here's how to sort on mobile: