In yEd, there are two ways to achieve the desired visualization:
Actually create two edges that are connected to a small (e.g. 1px in size) dummy node. Set the desired arrow at one of the edge endpoints connected to the dummy node instead of the endpoints connected to the original source and target node.
Create a raster image or vector graphic of the desired arrow. Then add an edge label to your edge, set the arrow image/graphic as the label's icon, and move the label to the desired location along the edge.