Thanks for joining this thread, NorthStar10.

Let me share an additional idea of why we don't recommend using categories when tracking inventory for multiple warehouses in QuickBooks Online. Here are some reasons as mentioned by the previous replies.

• Unable to run a Valuation report by Category
• Unable to run a report by Item that includes Category
• You're unable to know how much of an item or total you have in all locations

In the meantime, you may consider looking for a third-party app to track your inventory for multiple locations. 

I can see how this feature would be helpful for you and your business. Rest assured that I'll pass along your feedback to our product developers. They're always looking for ideas from users on how to improve QuickBooks Online (QBO). They might consider adding this in their future product enhancements.

If you have any other questions, please let me know by adding a comment below. I'll be around to help.