To Add a Control Point to a Curve and Maintain the Shape

Place a B-spline curve using the B-spline by Points tool (Drawing > Home > Placement > Create Curves split button).
Select the Edit Control Points tool ( Modeling > Curves > Modify Curves ), and select the Change No. of Control Points icon.
Enter the number of control points in the To field.
Select the curve.
Enter a data point to change the number of control points.
The number of control points is increased but the shape of the B-spline curve is preserved.