I changed my Mystery board after the outline was made. How do I update the outline?

From version 1.9.22, use "Fit the outline to the board". While the outline of a new mystery waits for your approval, a band above it offers "Plan the mystery" (it opens the Mystery board) and, once the board is planned, "Fit the outline to the board". For a book that is already written, the same button is at the top of the Mystery tab in the Codex. It rewrites the chapter outline so each clue, red herring and clearing sits in its chapter and nothing hints at the solution before the reveal. The chapters keep their text; regenerate the ones that should follow the new outline. Save the board first, because it reads the saved board.