Polycurves can be split at a knuckle, by starting the action from the menu [Polycurves]→[Split Polycurve] or with the keys <Alt><P><S>, or from the context menu after clicking the right mouse button on a polycurve in the tree view. When a polycurve is selected, the user is asked to select the knuckle to split at. The polycurve is plit instantly.

Splitting a polycurve.