SoftEditCrv is not working as advertised for me.
Version 5 SR11 64-bit (5.11.50107.14545, 1/7/2015)
I start SoftEditCrv, click on a curve, click on the base point on the curve. Then I drag the base point. The curve only moves only a fraction of the distance which the cursor moves. In order to move the base point location to a new point I have to drag past the new point. This is fundamentally different than the description and animation in Help for SoftEditCrv. The animation shows the curve moving with the cursor. It also means SoftEditCrv is not particularly useful for editing a curve so that it goes through a desired point.