Start with the reader’s journey, then give each chapter one central question to answer. Under that question, note the story, evidence, teaching or example that will make the answer understandable. This level of detail is enough to reveal gaps without forcing you to write the book twice.
After arranging the chapters, review the transitions. Does each section prepare readers for the next? Are the same ideas appearing in several places? A structured outline is especially helpful during developmental editing because it allows you and your publishing team to discuss the whole book before polishing individual sentences.