Cable assembly drawings are essentially mechanical drawings. The electrical connections are secondary to the mechanical construction, and are usually just listed in one or more tables (one for each connector) off in a corner somewhere. While you can use your schematic tool to generate the BOM, the primary drawing is best done in a mechanical drafting tool.
Think about what the person who is going to construct the cable is going to need, if all he's handed is your document. He needs to know
- what cable to use
- what connector(s) to use
- what other elements, such as heat-shrink tubing, need to be incorporated into the assembly
- what tools need to be used
- how much cable to cut off the reel
- how to strip or otherwise prepare the ends of the cable
- what the assembly sequence for the connector is
- how the pins of each connector are identiified1
- finally, which wire in the cable goes to which pin
For simpler cables, all of this information can be put into a single drawing. For more complex cables, there might be several drawings and a separate bill of materials.
Initially, you might be making prototype cables yourself. But if the product goes into production, you'll be handing this task off to another department or a subcontractor, and these details need to be precise in order to avoid expensive misunderstandings.
1 Note that it is important to be explicit about how YOU identify the pins of each connector. The manufacturer's own drawings can be surprisingly ambiguous or confusing.