You can drag the edges around, creating Bézier curves1). That is, the edges don't have to be straight lines anymore. You might want to use this feature in two situations:
- If you need more than one edge between two nodes:
- If it can help you in the overall layout
To move the center of the edge, drag the little circle in the middle of the edge and drop it on an unoccupied spot.
To change the edge back to the line, right-click the circle in the middle of the edge and select 
Restraighten
1)
In versions 0.113 and higher
MultiNet (Multilayered Extended Semantic Networks) is developed and maintained
by Intelligent Information and Communication Systems Department of FernUniversität in Hagen.
by Intelligent Information and Communication Systems Department of FernUniversität in Hagen.