Yes, you can reshape polylines and polygons by moving vertices or adding and deleting vertex points. 

For example:

1. Right click over a polyline or polygon and click Reshape. Each vertex in the polyline or polygon is identified by a small square around it.
   
2. To add a vertex point in the line, hold the CTRL key down (a + appears next to the cursor arrow), and then click where you want to add the vertex. A new vertex is added at that location on the polyline/polygon.
   
3. To delete a point, select one of the existing vertices and press the DELETE key on the keyboard. It is deleted.
   
4. To change the shape, select any of the existing vertices and click and drag it to a new location.
5. Press ESC on the keyboard to exit reshape mode.

 Additional information about the reshape command can be found in Surfer's help here.

Updated November 13, 2018