Draw an arc with the 3-point arc button in the sketcher
Draw an arc by clicking its start, its end, then a point it passes through, and close three lines into a shape with one curved edge.
Edit Panel Design's sketcher: the 3-point arc button (icon '3point arc', tooltip 'Draw arc by bending a straight edge') draws an arc from three clicks: its start, its end, then a point the arc passes through.
Closing three lines with the 3-point arc button gives a shape with one curved edge (start (60,560), end (260,560), through (160,520): radius 145).