Select the Edit/Measure Tool.
On the left-side pop-up, select “Points”.
Click on the “+” midpoint vertex on a segment.
Two new vertices will be added. One new vertex will be on each side of the midpoint vertex.
Click and drag on one of the new vertices.
Click and drag on one of the two handles. Dragging one handle will move one side of the curve. Dragging on the other handle will move the other side of the curve.