retrieving grouped delivries number

Dear Expert,

I can find a grouped delivery number in transaction VT05.

the protocole displays a "protocole group" number and all the grouped delivries.

Each delivery has a different shipping number.

I'm looking to put that grouped delivery number in front of each delivery or shipping number.

There's no way I could find a table with this grouped delivery number.

querying VBSS-SAMMG with my displayed number will not return any delivery numbers it groups.

Extracting VBSS-SAMMG numbers & VBELN together, shows that VBSS-SAMMG doesn't match (LIKP/LIPS - VBELN).

Is there any way I can identify a common information between grouped deliveries ?

Thanks