[iOS] How do I add a tab into a playlist and change the order of tabs in a playlist?
2. Tap the three-line menu in the top right corner and choose a playlist

You can also do it right from your playlist:
1. Open a playlist
2. Tap "+"
3. Choose from your saved tabs

In order to rearrange tabs in your playlists:
1. Open a playlist
2. Tap 'Edit'
3. Long-tap the three-lines button next to the tab you want to move
4. Tap "Done"