Security ID Number in Posted Document

Dear TRM experts,

I’m trying to post a FI document using transaction PMVM (Variation Margin Run), but when I check the document created, there is no reference for the Security ID Number used.

In other transactions that used the contract number, such TBB1, the contract is always in the field BSEG-VERTN.

Does anyone know if there is any possibility to post the ID Number in the document (BSEG or BKPF)?

I need this information to use a Substitution in the Account Document, and without the Security number there is no reference to use.

Regards

George Passini