This feature reminds me of the core module in Drupal called “Book”. There is an overview doc of it at Client Challenge, which itself is a work in progress, but the that section itself actually uses the module; Drupal docs are various “books” in this sense.
The book module is why I fell in love with Drupal 5 (our relationship has… cooled since then 
), and for some reason I’ve never seen their implementation copied into other systems; even WordPress doesn’t have an ordered structure out of the box (unless your order is by date).