true if interactive adding/removing of link segments allowed; false if not.
You can insert new link segments interactively by clicking and dragging a point of a selected link's segment. For polyline-style links this creates one additional segment by splitting the existing one into two parts. For cascading links there are two segments inserted, keeping intact the alternating pattern of horizontal and vertical segments, each orthogonal to its neighbors.
Segments can be merged by moving their joining point until the angle between reaches certain threshold value. In case of cascading and Bezier links, segments can be merged by placing adjacent control points close to each other, as set in MergeThreshold.
This property also affects how users can change the orientation of cascading links. For more details see CascadeOrientation.