
If you are not in curve editing mode, double click the continuous line to edit it.
) and dragging it to a new position changes the point location.
The continuous line is yellow, has a red handle at the selected point and two dull red lines with circles at the end, indicating the tangent direction and magnitude.

The middle points are selected.

on the Status bar so
is displayed.
on the Status bar enter 100 150 0 and click enter. The middle points are moved.
You can also use the Position dialog instead of entering coordinates.
) and dragging it to a new position changes the point location.
). Dragging it to a new position changes the continuous line to a Bézier curve. 
Releasing the mouse button gives:

For more information on editing tangent handle see Editing a Bézier curve.