Unlike other types of transactions in Plus, once an inventory transfer is recorded, you can't change it.
If you've entered an inventory transfer that you need to change, you can do one of two things:
If you need to remove the effects of an inventory transfer from your Plus records, you can enter a new inventory transfer that completely cancels the incorrect transfer. For example, if the transfer you want to remove is for a reduction of 20 gadgets, create a new inventory transfer of 20 gadgets (be sure to enter a positive quantity) to cancel the incorrect transfer.
Transfer Inventory Overview - Changing, removing and reversing inventory transfers