Stitch it!
Couching is an embellishment technique where a cord or yarn is stitched to the surface of fabric for added color and texture.
Originally a hand technique, it has been adapted to the sewing machine. Freemotion Couching Foot #43 holds the cord in place for stitching and with the feed dog of the machine lowered, allows the freedom of movement to follow any design, motif, or pattern.
See tips for stitching.