Is there a way to combine lessons from two different courses into one single course?
Did you upload them both? If so, yes. When you go to edit the lesson you change which course it is in.
Yes, as @noxialisrex mentioned, on the Edit Lesson page, you can change the lesson location and move it to any course you want. You will need to move each lesson separately. At the moment it’s not possible to merge two courses or move more lessons at once.