The Tiny Notebooks system assumes that project management is innately untidy. Giving each subject its own notebook makes it easier to shuffle between them, which is very well suited to an environment where you must change your focus with little warning or cannot reliably make planned progress in any particular project. This chaotic pattern describes software development (where fixing a critical bug may override project plans, and the best-laid project plans can be derailed by discovering pieces that need to be rewritten first), creative work (where the ideas just don't flow for one thing, and just do for another), home projects, and almost any work style where you feel confused and overwhelmed.
The idea of chaos management is to face the reality that this is just how your projects are and no organization system will suddenly make work flow easily in an orderly, precise manner. Chaos management attempts to keep track of the urgent things and the fixed-time things (appointments) first and foremost so they aren't lost in the shuffle, provide short-term work items that will make real progress so there is always something to go back to and do, and record what work was done, regardless of whether it was planned or not, for the benefit of any outside tracking (like weekly status reports for a supervisor) or for personal emotional health, because it is very difficult to keep track of just how much you really are dealing with when you're focused on what remains to do.