Hi,

This may be difficult or may be not possible from the studio,  if possible you can try the same from the code side, or without any changes, this can be easily achieved by creating two products with name Freight and Insurance, add those two the order lines and eventually it will sum up to the sub total.

If you don't want to handle it as above, you have add two new fields to the sale.order model and to record the freight and insurance charges, then you have to modify the current compute function for the subtotal and total field to adapt the value from two new fields. Related changes has to be done inside the invoicing model also, as the values has to be passed to the created invoice.

Thanks