Hi there, JBEL.

Building assembly or Inventory Assembly feature is currently unavailable in QuickBooks Online. You'll want to use a third-party app that offers inventory assembly and sync it with your QBO account. Here's how:

1. Go to the Apps menu, then proceed to the Find Apps tab.
2. Click Browse category and select Track Inventory. 

If you're referring to bundles, check out these articles for more details:

• Introducing QuickBooks Bundles and Reorder Points
• How to Use Bundles
• Add Inventory Products in QuickBooks Online

Don't hesitate to reach out to us again if you ever need with QuickBooks again.