Creating conginuous curves (CC) in IQ is done with the Line Pattern function. You can use any pattern that has the start and stop points on the same plane to create your design, allowing you to do "line dancing" with IQ. The steps below are for CC, but you could choose any design other than an arc. IQ will inform you if you've chosen a design that isn't appropriate for Line Pattern.
Get into the Line Pattern creator in IQ
Touch the Pattern button, and IQ will take you into the Pattern Selector screen (where your catalogs are).
In the Geometric catalog, there is a shape called arc. Select this and touch Continue.
IQ will take you back to the Line Pattern screen, where you can now sample points along your seam to place the curves. You'll notice you have a Pattern Height button and the height defaults to 2.0". In most cases that's too high, so make sure that is adjusted to what you need for your quilt.
When you sample points, only sample the intersections where you want the arcs to begin and end. You'll get infinitely better results if you can make your curves cross, rather than bouncing in and out of points/intersections. To make them flip over, touch the Flip Y button, and your next arc will flip over the other direction.