Make a small cable clip I can screw to the underside of a desk. Overall footprint about 40 mm by 25 mm, height about 12 mm. The bottom is a flat plate with two countersunk screw holes (for M3 screws) near the corners, spaced about 30 mm apart center-to-center. On top of the plate, add two parallel U-shaped channels (like shallow tunnels open on one side) so I can snap in two USB cables side by side; each channel inner width about 6 mm. The clip is one solid plastic-looking part with no moving pieces. Outer corners slightly filleted so it is comfortable to handle.