I edited my chapters after creating the index. Are the page numbers in the index still right?

Yes. From version 1.9.15 the index never stores page numbers or positions. BookyAI saves only the list of headings you approved, and finds every place they are mentioned again from your text each time you export and each time you open the Index page. Edit a chapter, add chapters or reorder them, and the page numbers in the next export are right without doing anything. If you added new chapters, the Index page shows a button "Read N new chapters": it looks for new headings in those chapters only and keeps every decision you already made.