All lesson related settings can be found here.
Classic Editor: If you enable this option, you will see an icon on the top right corner of the lesson editing option. That option enables you to see the lesson content on a separate screen and use page builders if needed. See this tutorial to know about to process in detail- Using Page Builder for Lessons.
Automatically load next course content: This works to create a seamless experience for the user. If you enable this, the next lesson will automatically load after the current content is finished.
Lesson Permalink Base: Here you can define the slug for all the lessons.