Is there a way to group content like a playlist in a wix database, for example: My Playlist and then you add the content within that playlist.
You can add music already in Wix with Wix Audio:
https://support.wix.com/en/wix-audio/wix-music-basics
If you want to reference fields from different datasets:
https://support.wix.com/en/article/about-connecting-multiple-database-collections
https://support.wix.com/en/article/working-with-multiple-item-reference-fields
https://support.wix.com/en/article/displaying-content-from-multiple-database-collections-using-reference-fields-4034931
If you want users to be able to pick their music and group it all into one field in a dataset:
https://www.wix.com/corvid/forum/community-discussion/multiple-checkbox-s-submit-to-single-database-field-solved
https://codequeen.wixsite.com/checkboxes
https://codequeen.wixsite.com/checkboxes/on-click-code