Whether it is on a curriculum, course, or lecture view—a green progress bar will show you how far you are in a particular course or lecture. Furthermore, a progress percentage is also shown on the right side of your screen.
This is how it looks like on course level (example Anatomy):
And this is how it looks on lecture level (example Head and Neck Anatomy):
Likewise, you can also track your performance in the quiz questions. Here, however, the spaced repetition learning approach shows the red color as an indication of questions due today, while the green color indicates questions which have been memorized:
Similarly, you can keep track of which textbook articles you've already read: