Outlines are IA by Christopher Butler:
The text-outline as an information architecture tool is useful when evaluating the effectiveness of an existing visual design. Whenever I look at a page or screen, the first thing I do is scan it to understand what kind of information it contains and how that information is arranged.
I’ll plug all sorts of things into Workflowy (my outliner of choice) to see the raw structure. And then drag the bullets around to remix and re-organize.