You are correct. You cannot move the markers directly by dragging. What I do is place the playhead where I want a marker to go, copy the timecode in the Canvas, open the marker to be moved, and paste the timecode into the timecode start field. When you close the marker and it will move to the desired time. This is tedious, but it’s the only way I know to move markers.
Lee Berger
http://www.leebergermedia.com