New points (vertices) can be inserted into polylines.
An individual point can be selected by holding the Shift key while clicking on a point on the map. After selecting the point it can be moved to a new location. Hold the Ctrl key while moving to keep the point aligned vertically or horizontally. If the polyline matches a sample area, then the matching vertex in the sample area will be moved as well.
An individual segment can be selected by holding the Shift key while clicking between two points on the map. After selecting the segment it can be moved to a new location. Hold the Ctrl key while moving to keep the segment aligned vertically or horizontally. If the polyline matches a sample area, then the matching segment in the sample area will be moved as well. You can also set the exact length of a line segment by right-clicking on it.