I attempted a more dramatic approach: create the new Plane Shapes based on the properties of existing Plane Shapes, then delete the existing Plane Shapes:
For Each shapeObj In doc.PlaneShapes
If (shapeObj.PlaneClass.HasOverrides) Then
FORMA = shapeObj.Geometry.PointsArray(epcbUnitCurrent)
Call doc.PutPlaneShape(shapeObj.Layer, 1+ubound(FORMA,2), FORMA, shapeObj.Net, shapeObj.ObstructType,,,, Nothing, epcbUnitCurrent)
Here I achieved my goal: "Override" status has been reset. But the new problems have arised:
There is no PlaneClass among the properties of doc.PutPlaneShape() method.
And with the advent of PlaneClass mechanism, the HatchPattern, HatchWidth and HatchDistance among the properties of doc.PutPlaneShape() method look obsolete.
Also, doc.PutPlaneShape() method has two duplicated properties: ObstructType and RouteObstructed.
So I think it is dangerous to use the above approach, for resetting "Override" status.