Hi,
If you are working with STO between storage locations of different plant, nothing to do with the configuration of STO between storage locations, instead you have to configure STO between plants. You can issue from Plant A storage loca A with shipping point A with normal STO PO between plant to plant. Insert the receiving plant (plant B) and receiving storage location in STO PO.
Note: In Configuration you have to assign the delivery type NL and the checking rule.
Also, you have to maintain the preferred shipping point in the Logistic execution configuration as below.
Hope its helpful.
Regardsa
AKPT