You can bookmark as many pages as you wish in a Calypso course.
Simply click the blue ‘Bookmark this Page‘ at the top of the page you wish to bookmark. After you add a bookmark, ‘Bookmark this Page‘ changes to ‘Bookmarked‘ and a bookmark indicator appears in the unit navigation bar at the top of the course page.
To view your bookmarked pages, click on the course ‘Home‘ tab at the top of the course. You will see a list of Course Tools on the righthand side of this screen. Select ‘Bookmarks‘ to view a list of all bookmarked pages.
For a detailed view of how bookmarks work you may wish to review the edX help center here.