Curved arrows / arrow shapes

To draw a curved arrow, use "Draw a Shape" under Insert -> Shape and draw a curved line. Set it's "Fill" to "None", change the "Stroke" to "Line" and increase the line's thickness. Set an arrowhead for one of the endpoints and you've got a curved arrow that you can then make as thick or as thin or as curved as you need.

If you click this line once, pause, then click it again, you will see the red dots that indicate the control points. Click one of those red dots and you will see the controls for the curvature of the line. Use these to fine tune your curve.