At the user level, you can expand or collapse Lesson content from your personal view.
Once you have a Course selected in the Courses and Groups dropdown menu, click the Lessons link in the Course Navigation bar.
Collapse Lesson Contents
Click the Expand/Collapse arrow. This will only hide the Lesson contents from your personal view.
The Lesson will stay collapsed until you decide to expand it. You can show Lesson contents by clicking the Expand/Collapse arrow.