Reviewed the Extrude, ExtrudeFunction, ExtrudeDependency, FacePickerPlane classes.
Improved the FacePickerPlane code so that it doesn't inform the user about the selected plane at every mouse move. It informs only when a new plane is selected. The highlighting disappears when the mouse goes out of the selected plane. Didn't solve the flickering caused by the change to Neutral Point to Local Context, studied and understood the problem will find a solution later.
Will continue with making an Extrude on the face of another Extrude.