You can customize chapter headers by using the Chapter Heading Settings in your Theme. These settings allow you to choose which details you want to display in every chapter, such as chapter number, title, subtitle, and images.
You can make changes to your theme on the Formatting Tab by clicking the three dots next to the theme name and selecting Edit or Edit as New Theme.
For more details on how to set up or adjust your theme settings, you can refer to this tutorial: https://www.atticus.io/create-a-custom-theme/ It provides detailed instructions and tips on creating and modifying your theme.