From L Nguyen Huu on 2017/09/30 17:18:26 +0000
Audio files from custom sources (Google Drive, Downloads, etc.) cannot be added to playlists. Instead, selecting the folder icon in the playlist menu then choosing a file from e.g. Google Drive will reset the entire playlist and replace it with a single file. So if you want to create a playlist entirely from sogs on Google Drive because you don’t have much space on your smartphone but you know you’ll have an Internet connection every morning, you can’t.
Copied from original feature request: http://urbandroid.uservoice.com/forums/264867-sleep-as-android/suggestions/31691308-add-audio-files-from-custom-source-in-playlists