In a purchase invoice with an item charge, the charge must be assigned to either a purchase order receipt, sales order shipment, purch return shipment, sales return receipt or transfer receipt.
This last option (transfer receipt) is only possible when the transfer order is received.
But when the transfer receipt will be posted a few weeks after the transfer shipment, that means a purchase invoice that is entered shortly after the transfer shipment cannot be posted for a few weeks until the transfer receipt has been posted.

Please make it possible to assign a charge to a transfer shipment as weel or instead of a transfer receipt.

That would mean that after posting the purchase invoice, the item charge should then first be linked as value entry to the positive item ledger entry (on the transit location) from the transfer shipment.
And on posting the transfer receipt, the value entry must be 'moved' to the positive item ledger entry (on the destination location) from the transfer receipt.