While it is currently possible to return to either the activity (from the Assignment name) or the Canvas home page (from the course name) in Speedgrader, these helpful links are not apparent. I would suggest to add a Home icon in the top left of the Speedgrader beside the existing icons (Gradebook, Mute/Unmute, and Settings). I have a mocked this up in Photoshop:
OR to add underline styling to the course and assignment names. Please see this Nielsen-Norman Group article for a user experience best practice on this issue: Making Clickable Elements Recognizable. Currently these links underline only on hover, so instructors may not notice that they are hyperlinks, and the instructor may be spending many minutes (exponentially) navigating back to their Canvas course using either the Courses flyout menu or the Dashboard. Both take several seconds to load.