I drew up a quick cable comb when I was redoing my rack recently, and I decided to upload it here and try the new parametric design features. The example model uses a 7mm cable size, this was for some thick RG6 coax. 

5.2mm and 4.8mm were used for two different types of network cable I have ran around the house

Due to the quick and lazy way I patterned this and because of the offset row look I wanted you will have an empty slot when giving an even number for cable quantity.

You can modify the throat width modifier to change the opening of the cable slot, if you want to close it up for soft cables or open it up for hard cables. The percentage relates to how open the throat is, so 0 is closed and 100 is open

I printed my example with PETG and 4 walls so it could flex quite a bit to get some of the harder cables in.