Specifically, I’d like to see if a “former barcode” was added. But other changes as well like updated renewal date, or name changes, etc.
Sadly, no. You can see that a patron registration was modified through the last modified dates and within the PolarisTransactions database (TransactionTypeID = 2002). But as to what was modified? That’s murky. To the PolarisTransactions database, the modification of the barcode or addition of a former barcode is just the same as renewing the registration and updating the expiration and address check dates.
The only way I can think to check for things like the addition of a former barcode would have to do with snapshotting your PatronRegistration table every so often, and then running comparisons between your snapshots and your live data. That’s a faff, for sure, but it is doable.