Here is a cut and paste explanation from carbuyer:
"Under WLTP, the individual options fitted to a car will factor into the test. Each and every option will be given a CO2 figure, largely influenced by its weight, aerodynamic penalty or the amount of power it draws from the engine. This will impact heavy items such as panoramic sunroofs and larger alloy wheel sizes in particular.
While it doesn’t spell the end of individual options as such, a model could have hundreds – or thousands – of different CO2 figures depending on the number, type and combinations of options chosen"
Maybe this is the reason you cannot now add individual options?
"Under WLTP, the individual options fitted to a car will factor into the test. Each and every option will be given a CO2 figure, largely influenced by its weight, aerodynamic penalty or the amount of power it draws from the engine. This will impact heavy items such as panoramic sunroofs and larger alloy wheel sizes in particular.
While it doesn’t spell the end of individual options as such, a model could have hundreds – or thousands – of different CO2 figures depending on the number, type and combinations of options chosen"
Maybe this is the reason you cannot now add individual options?