[cflsystems]

I agree - this is huge limitation and exists in every shopping cart.

Most likely this has not been implemented in XC5 - XC4 has this and many other features missing from XC5.
The only way to get it is to either order customization service or wait for next 2-3 releases before you can use it (but you must post in ideas site and vote for it and it has to be considered as something important by QT).