I explored the same venture quite some time ago. There is nothing complicated about the cable, even the cable connectors are available for purchase through various retailers online. But what I do recall is that a couple of the pins carried a bit more current than others, and a few weren't even used. So changing out the cable would be a little more complicated but shortening it with the factory one would be quite easy as long as you ensure that you reconnect each lead back to exactly the same pin position.
If you're curious why Lumin doesn't just say "Sure!" to a shorter cable request its because they don't manufacture it themselves. They bring it in, in bulk, in the factory length and asking their supplier for a single shorter length, I assume, isn't worth the trouble or potentially additional cost. A factory cable replacement cost $200 USD last time I checked.