This video demonstrates the relative ease of pulling together a custom cable in the Zuken E3 tool. This video draws an Ethernet cable consisting of two RJ-45 connectors and a CAT-6 cable.
Though Zuken E3 has much of the look and feel of a schematic tool that one would use for PCB schematic design, this tool was constructed to handle both the mechanical and electrical aspects of system-level design. One must keep in mind that EDA tools are geared for electrical schematic designs, dimensionless by their nature. This is why it isn't easy to make a cable design with any intelligence (i.e., properties, parameters, attributes, etc.) in an EDA tool.
The E3 tool is truly a system engineering tool; cabling is simply one of several core capabilities.
We have a webinar recording that goes with this demo video, and you can find more information at http://ninedotconnects.com/webinar-request-cable.