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