add identity column (or something??) to PSA table?

I want to add an identity column or something that behaves like an identity/sequence to a PSA table.  How do I add it? 

I tried to add the column Post-Create SQL but BimlFlex doesn’t allow that.

Unfortunately there is no built-in-function to add a sequence identifier to PSA tables.
        
The normal PSA uses the defined source key to persist and historize loads.