Have the breadth as a summary page perhaps? Like when you open a book and it's effectively the list of chapters. Then have the 2l tiers as your chapters and the

Have the breadth as a summary page perhaps? Like when you open a book and it's effectively the list of chapters. Then have the 2l tiers as your chapters and the 3l tiers as the subheadings in those chapters? Don't know whether that's what you're doing at the moment :)