To Insert a Knot Point in a B-spline Curve

Select the Edit Knots tool ( Modeling > Curves > Modify Curves ).
Select the Insert Knots icon.
Select the B-spline curve.
Graphics display the proposed knot point on the curve. Its position is controlled by the pointer.
Enter a data point to place the knot point.
(Optional) Press <Ctrl+data point> to add more knots.
Enter a data point to accept the insertion.

Inserting a Knot Point. Method = By Points, Control Points = On

Inserting a Knot Point. Method = By Parameter, Knot Value = 0.5, Control Points = On