There are three ways to switch between your courses from within the student course platform. The first two are shown in the GIF below.

The first is from the new Dashboard, which displays all of your current courses as cards. You may click on any of the courses from here.

The second way is to click "Courses" from the global navigation menu on the far left-hand side. This will display a popup with links to all of your current courses.

The third method is to return to your Dashboard page via the button at the top (as sown below), from whence you can go to any course in your account.