Hi there, @veronicas.
Thank you for joining this thread. Allow me to chime in for a moment and share some insights about adding a sub-item on transactions.
As mentioned by my peer, choosing and adding a sub-item on the Invoice screen will let you see its main item. However, this information will not auto-populate on the printed transaction template. It will only show the Sub-item you've chosen.
We don't have updates yet about this, but we'll be sure to cascade it through email notification. For now, you can visit our QuickBooks App Store. There are a variety of applications you can choose from to help you in customizing your invoice transactions and item views.
Let me know if there's anything else you need. Just add a comment below or visit the Community again. We'll be happy to answer all your inquiries.