Hi there, @jmkmpf.
The option to create an item with a percentage is unavailable in QuickBooks Online (QBO). For now, we can only track items based on their flat rate.
I can see how this option would help you in managing your invoices. Thus, I'll note this as a suggestion to improve your experience in the program.
I'd suggest looking for a third-party application to help you with this task. Simply go to the Apps menu and select Find apps. Then, look for the app in the Search bar.
Moreover, you can customize the appearance and layout of sales forms in QuickBooks to help enhance your business communications.
If you have additional questions about managing your invoices, just add them to the thread. I'll be here to help you out. Have a good one.
