I just noticed that there's no "Add a chapter" option in the Project context menu. This is presumably because a Chapter is really just a Folder. Calling it a Chapter gets the user oriented, but then subsequent Chapters will be created by invoking "Add folder". This could cause some confusion. At least, it prompted me to try to explain it!
It's also worthy of note, as I get more familiar with this UI and document paradigm, that a folder is truly just a folder, not a chapter or a set of notes, until it starts to contain things. The user determines what a folder really is.
Although the demo doc gave me the impression that AS is based on chapters, it's really a framework for managing Scenes and Notes (etc.), by means of Folders. So a logical approach is to name top-level folders Chapter 1, Chapter 2, etc., but that's just the writer's own choice. Top-level folders could instead be Part One, Part Two, etc. And one could put ALL text blocks within a Chapter or Part folder, or in a separate folder on that level.
This approach requires users to consider the structure of their text. In the magnificent old pre-Windows formatting document editor Manuscript, from Lotus, all text was just called a block, which was equivalent to a paragraph. Short blocks got formatted as headings, longer ones as paragraphs. Since the whole model was hierarchical, indentation was used to determine a block's position in the matching format hierarchy. It sounds weird, but it was very simple, and worked amazingly well for almost all conventional document development.
This is the kind of flexibility -- mainly in the Tree -- that originally drew me to Scrivener, although I found S to be weirdly hard to grasp, due to the added specialization of various doc structure elements. Or at least it did confuse me. The document export system was so confusing that as a long-time former programmer and software architect, I still gave up trying to figure it out.
As I write this, after importing a 150,000 word novel in over 90 chapters, I'm really excited that the document model of AS may be so simple and flexible that I will soon find it indispensable.