The main purpose of the Archive feature is to set aside Setlists that are no longer used in a separate section (and thus declutter the Setlists list)

You then have the option to offload them in order to save storage space and reduce synchronization calculations.

You can either access the archive option by pressing a Folder row or inside the Folder view with the "..." button.

The archive folders are then stored in a separate section, accessible by tapping at the bottom of the Setlists list:

These archived folders can then be unarchived from the contextual menu of a Folder or inside the Folder view ("..." button):