If you're on the go and have a new song that you'd like to add directly to a playlist folder, you can follow these easy steps:
1. Open the playlist folder you would like to add a song to and click the '+' button in the top right.
2. Then select the Song option. This will create and open a new song that you can name, add lyrics to, add members to, and add recordings to.
Note: Currently the functionality to move songs from folder to folder on mobile does not exist yet. So if you need to rearrange songs in your catalog, you'll need to be on your computer.