I appreciate you sharing this matter in the Community, @tarengarone. Currently, QuickBooks Online does not offer any built-in feature or automated tool to migrate or convert historical data from Tags into Locations.
The tags and locations are separate tracking tools with different data structures, your historical transactions in tags will remain that way. For now, you can only stick with your idea, which is updating them manually.
Aside from locations, you can use the custom fields, however, you still need to perform it manually.
Regarding your concern about the absence of the feature. To clarify, Tags have not been removed from QBO. The existing customers currently have access to this functionality, while it's not yet available to new customers.
Let us know if you have further questions. We'll be right here to help you any time.
