Scenes are the structure that lets you change a level using the Scenes pane in the in-game ST interface. It unlocks the ability to build stories that have areas that evolve within a single evening's game. The process can be challenging, but it is well-worth the effort. Your players will gasp at your supreme ST powers if you can pull it off. ;)
Making your Redemption expasion easy to install is critical to the success of any release. Publishing Expansions is a guide for making releases as plug-and-prey as possible, and should help you take some of the kinks out of the process of distributing your expansions, be they maps, skins, chronicles, or, jeeze, practically anything!