Overwrite Freight applied on order line at shipping

Hi

Is it expected functionality that a Freight charge entered on the sales order line cannot be overwritten at time of shipping?

I am using a Freight Modifier to apply Freight to my order. I use the modifier in conjunction with the Freight item too allow for the application of tax on our invoice. Only the modifier appears on the order. The Item only appears ib tge invoice.

I apply a Freight charge direct to the order line at time of order entry and then I attempt to overwrite this value at shipping using the cost to charge method.

The cost to charge works fine if the Freight is only applied at shipping and where there is no value entered at time of order entry.