Hello, Incausa. 

The option to add the B2B portal to the inventory is currently unavailable. You may want to look for a 3rd party app to connect your b2b portal to the inventory. In the meantime, I recommend sending Feedback to our engineers. This way, they can review your suggestion and may consider it for future updates.   

1. Access your QuickBooks Online company.
2. In the upper-right corner, click the Gear icon.
3. Under the Profile column, select Feedback.
4. Enter a brief description of your product suggestion, and then click Next.
5. Type your email address.
6. Once done, click Send Message.   

You'll want to track your suggestion through this website. You can also take this article for more details about inventory management: Add inventory products in QuickBooks Online.

Please let me know if you have additional questions. I'm always here to help. Stay safe and well!