How to consolidate two different legs Shipment using bulk plan

Summary:

We have business requirement to consolidate the two different legs shipments into 1 Shipment to make them as Round trip shipment.

Highlighted below in the Green should be able to consolidate together using bulk plan which is not happening but when we try to manually merge those 3 shipments together after bulk plan completion, I am able to merge them.

How can make this change to allow system to do it at time of bulk planning ?

Below is the multi-leg itinerary for entire legs:

Leg1: Is for below routes:

• CrossDock to supplier1 —> Supplier 1 to supplier 2 —> Supplier 2 to CrossDock
• Leg1 has Leg classification defined as "