Can BookyAI plan the mystery of my novel for me?

Yes, from version 1.9.22. Open the Codex from the book's page, choose Mystery and press "Plan the mystery with me". You can write your idea in a sentence or two, for example "The vicar did it, to protect his daughter. The reader should suspect the gardener until chapter 8", or leave the box empty. Press "Plan it". BookyAI proposes a fair-play mystery from your idea and the book: the truth, the culprit, suspects with motives and alibis, real clues and red herrings in their chapters, a midpoint twist and the reveal. Anything you had already decided stays. Read it, then press "Use this plan", and save the board.