This clip drops into the holes in an ELFA vertical standard, and provides a small clipped-in area for cable management. Should be compatible with all other two-slot vertical standards (Rubbermaid, Closetmaid, etc). This uses my ELFA Hook Profile design, so it locks into the rails just like a solid-shelf bracket does.

Consider mirroring a few in your slicer of choice to provide cable management on both sides.