The six families
Almost every drink in the book is one of six structures wearing different bottles. Learn the six and the list stops needing memorising.
Sorted by what holds the drink together rather than by which spirit is in it, which is the move that makes them useful: a Negroni and a Boulevardier are the same drink, and no ingredient-based sorting will ever say so. The framework is the one set out in Cocktail Codex; it was not on the course, and the chapter goes through how to build with it.