I plan on doing some step-by-step walkthrough tutorials for the more advanced features that are not obvious.
The community is also invited to write up tutorials, documentation, and maybe videos of how to use MediaBox. I can't do this all alone, so naturally, documentation is always lagging behind.

How to make a playlist:

The items that can be added to a playlist have a button with three lines (looking like a list of items), and in MediaBox 0.96.5 the label "Playlist". When pressing this button, MediaBox appends the item to the currently selected playlist. You can select and create new playlists in the playlist viewer (second icon from the left on the menu panel). There you can also change the order of the items by dragging with your thumb (there's a grip area to the left of the playlist items).
If you press the "Playlist" button on a directory or album, all items within that directory get appended to the playlist at once.
Playlists are saved automatically, so you don't have to worry about that.