When merging courses in Canvas, the platform merges only the rosters, not the content (this includes student submissions). That is why it is important to merge courses before students submit any work, because their work in the original will not follow them to the merged course.
Also, for same reason as above (merged rosters but not content), choose a course that has content as the Parent (main) course. If you choose a blank course as the Parent (main), any courses with content that you merge into a blank parent will lose the content, leaving students viewing a blank course.
Once merged, the Parent course will be the main course, and the other merged courses will become sections (Child) courses of the main Parent course.
Canvas Course Merge Request form
