For example, If a Freighter picks up a good at a hub on dock #4 and brings it to another hub, I do not think you can drop the items off using another dock#. It needs to be #4 at the drop-off hub. It seems that you should be able to. i.e if you pick up a block from port 4 and bring that to another hub, if dock 4 is already used by another item/freighter you should be able to select dock 1 at the drop off. See my attached image. It seems that all you have to do is select Action:Load on dock 4 of the pickup hub and select Action: Drop off on dock 1 at the dropoff hub. However, though the Apply changes succeeds, the freighter does not drop off anything.