Hi Rafel,
All condition that you had mentioned forwarding agent, insurer, taxes is consider in the cost of Material, that to be purchase , absence of these condition would not reflect final cost of material to be delivered, taxes as per process can be deductible and non-deductible .
But if you want to exclude these conditions in PO ,then you have to create separate service orders for forwarding agent, and insurer and this will be followed by service entry sheet , after you can initiate for the invoice verification of forwarding agent, and insurer for payments.
If followed by this practice then one can not include the cost of insurance and forwarding/freight charges in to the material cost or can say we can not link the cost of Material PO and Service PO of forwarding agent, and insurer together, the both will treated as separately.
With Regards
Aditya