"Green Bar" on the right: It is the navigation menu that comes into focus once you click on it. You can focus on the content w/o getting distracted by the ToC.

"Green Bar" on the right: It is the navigation menu that comes into focus once you click on it. You can focus on the content w/o getting distracted by the ToC. :) To OP. Don't worry. It is intuitive enough (for me at least (-; )