Copying Lessons
You can find the copy button at the top right of your lesson in the editor (see screenshot):
After copying the lesson, you can go to the same shortcut area and move the lesson to a new course, or you can drag and drop the lesson to a new course if it is easier.
When you copy a lesson, it will also have references to all the original attachments and media that you had for that lesson. You can safely change attachments on the new lesson and it will not affect or break other copies.