The first and easiest method is to store two different size cables in the same cable pocket just by combining lengths that you won't be able to confuse (like 40" cables and 24" cables) and then listing both sizes on the included label. And if you need new labels, you can make replacements out of any heavy weight paper cut to 1/4" by 1".
Another option is to make plastic sleeves to hold each size or brand of cables. With these you can store multiple brands and sizes in each pocket - doubling or tripling your storage space!
Washi or similar tape,
permanent marking pen,
a ruler or measuring tape.
In the front pocket of this Deluxe case, the sleeve is too tall to allow the pocket to snap closed. But since the sleeve fits snug from side to side, I don't really need to do anything further. But if I want to snap the pocket closed, I will need to shorten the sleeve 1".