Thank you for getting in touch with us about your concern, accounts-saltoro.
I'll share some info about the feature and how you can do this in QuickBooks Online.
A bill of materials is a list of all the components you use to build a product. While we're unable to directly set this up in the online version, you can create items and add them as a bundle.
Once done, go back to New and select Bundle as the product type. Then, add the items you created. Here's a link for more details: Add product and service items to QuickBooks Online.
Furthermore, you can search for a third-party application that has the bill of materials feature. To see the lists of apps, you can follow these steps:
Kindly inform me if you have any additional questions about the steps above. I'd love to help you out some more. Stay safe.