Thanks for coming here today, president-lfm-om.
You can use the Custom form style feature and add a Custom field for your donors Parent's ID. I'd be happy to share the instructions below:
For more information about this process, you can visit this article: Customise invoices, estimates, and sales receipts in QuickBooks Online.
To test it, you can create a sample invoice for your donor and you will notice the added field for Parent's ID on the transaction. I've attached a screenshot for your visual guide:
If I can be of any assistance, please don't hesitate to leave me a comment below. Have a wonderful day ahead.
You're most welcome, president-lfm-om.
I'm glad to know I was able to help. Please don't hesitate to visit us again if you have future queries and I'd be more than happy to help. Wishing you and your business continued success.