The way it is done by most of the software that does support it is a tweak to the inventory control which allows you to “build” other items from a base inventory item. So if you have a 100 cables which are item A, you could have a set of 5 cables which are item B but are actually “built” using 5 of item A. When you sell item B it takes 5 of item A off your inventory.
I’m sure I’m not the first person to bring this functionality up. I recall having to build something basic like this in programming school. I am sure it is way more complicated especially when integrating existing systems.
Even still, I wish SixBit worked at making their program the strongest possible tool for eBay instead of moving from platform to platform. I’m not opposed to the other platforms or anything…I just never felt like the development of the eBay version was finished.
Oh well…some day I guess.