Can reviewers adjust the chapter splits manually if they disagree with how it grouped the PR, or are the chapters fixed once generated?

We don't support that currently, but would love to see examples where you disagree with the chapters so we can figure out the best interface

You can regenerate the chapters anytime, but it might lead to similar results as the first time

We're also planning on adding functionality to support some sort of CHAPTERS.md file that lets you specify how you want things broken down!