Improve authoring tool

[mkpelletier]

When working with several pieces of nested content, especially with in the book, the authoring tool becomes very cumbersome due to the indentation of the content, leaving you with very little space in which to work. I really like the resulting content of the interactive book, but creating it is not a nice experience, even on a wide screen monitor. Would it not be better to use pop-out editors or modals instead of indenting?