You can't directly duplicate a page or chapter within Atticus at this time, but you can set up a Master Page and add as many of those as you need.
Design Your Page: Start by crafting a page within a book you're working on.
Save as Master: Once satisfied, click the three dots beside the page's title in the left navigation panel, then select "Save as Master Page."
Once the Master Page has been saved, you can add more copies of that page to the current book or another book:
To access your master page from another book, click the three dots beside "Add chapter," and select "Master pages.”
Simply drag and drop the master page where you need it to be in the left navigation pane.
You can learn more about setting up and using Master Pages in this tutorial: https://www.atticus.io/how-to-create-a-template/