Whenever you’re happy with the seem of the eBook, you can publish it. This does not publish your eBook to Kindle Direct Publishing, but makes the .kpf file and you will upload that file to Kindle Direct Publishing, in place of your Word file. That's why we advocate Atticus as https://maplepublishers.com/blog/is-it-essential-to-follow-the-trend-while-writing-a-book/