Thank you for posting here in the Community, @archer_104.
If you are referring to updating a new payee to the existing transactions by batch is currently unavailable in QuickBooks Online. And yes, you are correct that it needs to be updated by manually opening each transaction and select the appropriate payee.
You also have an option to run Transaction List by Vendor report to see the transactions that need to edit. Let me guide you how:
Go to the Reports tab, then in the search box enter Transaction List by Vendor.