Add CVs or edit points to the end of a curve
Extend a curve or curve-on-surface a certain distance
For curves-on-surface the Parametric Distance sets a fraction of the surface length in the direction the curve runs. For instance, a value of 0.5 extends the curve length by roughly half the length of the surface in the direction the curve runs.
Extend one end of a curve or curve-on-surface out to exact coordinates