Hello,

follow this steps:

1. activate "multi step routes" feature In Inventory App Settings


2. Open Warehouse B -> choose to deliver in 2 steps

3. Open "Routes" Tab in Inventory Configuration menu.
4. Choose Delivery route:

5. Change Rules to:

5.1. details of the first one:

Note: the default pick operation is from stock B to Output location b.So, you have to change it into WH A stock

5.2.  details of the second one:

6. create sales order from WH b:

7. Two Invenory transfers Details:

Hope it will help.

You can modify the delivery route by adding the below rules. The route would look for product availability in WH A and if unavailable will create an internal transfer from WHB to WH A

Pull from WH A to  partner location/customers; Delivery Oder Operation; Take from stock, if  unavailable trigger another rule

Pull from WH B to WH A; Internal Transfer operation; Take from stock