IB - how to execute a nymex heating oil crack spread?

can someone from IB explain why they do not offer the nymex (cme)crack spreads (heat vs crude and rbob vs crude) and the rbob to heat spreads on TWS especially when they offer every other illiquid contract out there? these spreads are native to the exchange and are active and liquid

any way to trade these spreads? i can not seem to get them to work in the combo trades

thanks

 

I tried to use a combo order but they don't support it. You can always leg in and out.