This is a device for those of us who don't like cable chains. When cable chains are removed on a larger x-y type printer, it can become difficult to arrange the cables so they don't drag onto the print surface, get caught by parts of the printer, or tangle with other cables, filaments, or bowden tubes. These "Cable Danglers" mount on a horizontal 2020 extruded bar and are very configurable for hanging cables toward the centers of where they might need to travel. The suspension is flexible, using "music wire" (sometimes also called "piano wire" -- even a thicker steel guitar string may be usable). The loop that the cable is suspended through has freedom of movement around the wire axis and forward and back over the bed, but it cannot twist (as that could cause cables to tangle on some printer head movements).
Music wire can be bought online or at some hardware stores (ask if they carry K&S tubing -- if they do, they likely have music wire). Choose wire gauge for the amount of flex you want. Flex can help to mitigate any possible sharp bends in the cable over the years, but stiffer mount can be better defined. I used 0.047" (1.2mm) diameter music wire, which works pretty well for suspending at a distance of around 10". The placement is arranged by the angle of suspension, length of the wire, and mounting position on the printer frame. The length of wire should be a little less than half of the span the carriage has to travel over. To cut the music wire, use the inner section of a care of gas pliers to shear it at the position you want.
The "rotary clamp" has a ring of openings on one side that go over small posts on the side of the "2020 mount" so that the angle of the music wire as it extends out can be adjusted for best position. The M3 screw that holds the two plastic pieces in the desired rotation also clamps the music wire in position on the rotary clamp.
This system works best with cable wrapped in 8mm "spiral wrap", such as https://www.amazon.com/gp/product/B07JXZ6KPB/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I added two alternate and preferred versions of the 2020 Mount part, which are easier to print (no brim needed) and require less plastic. They require the mounting screw to the 2020 extrusion to be on the same side of it as the 2020 Mount. Right and Left versions so you could use without them sticking above the printer frame. Use the original 2020 Mount if you need to screw in from top or bottom of the extrusion.
Also added is a smaller version of the hanger, if you want to minimize things that go above the top of the frame (like, when adding an enclosure) or just to keep everything small. The first main photo in this feature is with the smaller hangers and the smaller (alternate) 2020 Mount parts, as I think they look a little better.
To secure and control the ends of cables (particularly those running to RJ45 breakout boards) and minimize sharp bending there, also check out the Cable Strain Reliefs designed to work with this system -- https://www.thingiverse.com/thing:3624481
I hope someone finds this helpful, it has made printing simpler on my FT-5 printer.
any PETG but about anything
The "2020 mount" and "rotary clamp" should be printed with a 0.4mm nozzle and with about a 3mm brim, as there are fine parts in the first layer which may have problems sticking to the bed or otherwise needing detail. Do that and printing is pretty easy. The other parts can use a 0.4 or a 0.6mm nozzle and don't need brims. Depending on how well your printer handles bridges, you may need to run drill bits through some of the openings for screws and wires to pass. All screws are m3, except the m5 and m5 T-nuts that hold the "2020 mount" to a horizontal 2020 bar.
The parts that are meant to swivel (hanger, hanger mount) can be attached with nylock nuts not fully tightened (or dual nuts tightened against each other) so the plastic pieces can move, which also minimizes drag on the cable during movement. Or you could position them where you want them and tighten those interfaces if you prefer.