Can I add a stock location field on the product?

Hello there, TJB12.

You can add it under custom fields and is only applicable on the sales forms like invoices, estimates, and sales receipts.

This has a feature to assign transaction fields to specific sales forms. For the detailed steps, I've added these links you can check: 

• Create and edit custom fields in QuickBooks Online Advanced

• Customize invoices, estimates, and sales receipts in QuickBooks Online

For more references on how to manage your business with QuickBooks Online, you may visit this page: QBO Articles.

I'm just a few clicks away if there's anything else you need. Thanks.

@TJB12 

QBO doesn't offer the multi warehouse feature. You need to have an additional app to integrate with your QBO.