To be honest, I kind of feel this could be a bit better than it is, so I'm making it public domain and including STEP files, but it is still useful.

Extra Materials Needed

There is limited force you can really put on a printed clamp without lots of perimeters and more filament cost, especially with PLA creep concerns, and I wanted something I could print with low filament use. 

 My solution to this is to use poster putty for extra grip, it really helps just about any clamp hold.  I am not sure if this would be needed if you used PETG.

Some cables with smaller connectors might be able to pass through entirely. For those you might need to add something, like this doubled up extra thick hair tie.

I think those thick hair ties have potential for other printing related uses, they're multicolored, durable, and come in semi-standard sizes.

Features

The main feature is to hold a cable down on your desk, and additionally, it can hold cables going side to side, plus in the space between the screw and clamp body.

The Gridfinity base doesn't have magnets, and is largely there to make use of extra space, but having a defined place to set something is always nice. The padeye at the bottom will fit a paracord nicely.

Note: They don't tile! A 2x1 gridfinity piece will not fit 2 side by side. #todo!

The slot in the back is meant for things like shelf or cable labels, and can also be used to guide thinner cables if they are 3MM.  Just fold the bottom of a cardstock to make a lip

The nut is not a standard metric nut.  The screw threads are M24, but the nut body is 28mm face to face and 12mm tall.

Printing

It needs supports between the split on the front, but you don't really have to remove them, it's not in a visible place.

You have to be careful with infill and perimiters on the screw, long printed rods like to break at diameter changes if they are thin, although I've tried to prevent this.

I use PrusaSlicer, the 3MF file has everything in optimized orientations already.