The Save button in the top right of your screen is more of an account backup. This can be used to restore the entire account if anything unusual or accidental happens to your content.
Atticus will automatically save your work to the cloud, so the next time you start to write, it’ll be in the system even if you haven’t pressed that backup save button.
If you need a Word export, you can open your book and click on the book details panel at the top of the left navigation. In the popup that shows up next, if you scroll to the bottom you’ll see a .docx export button. Word does not have the ability to display the complex coding Atticus uses