In "Plan my book with me", my hand edits were lost when I asked the AI for a change. Is that fixed?

Yes, from version 1.9.24. Any text you change by hand in a proposal is marked "Edited by you", and it stays exactly as you wrote it when you ask the AI for a change, unless your request names it. For example, "Add a new chapter between chapters 5 and 6" adds the chapter and keeps every chapter you edited. If the AI's answer leaves out a chapter you edited, BookyAI puts it back. In an older version, agree to each stage once you are happy with your edits before you ask for more changes, or copy your text somewhere safe first.