It’s great to see you in the QuickBooks Community, jason93.
Allow me to share some insights about creating custom fields and how they work.
Currently, you can only add custom fields and manually enter the information each time you create invoices. While there isn’t an automatic way of entering data into the text, I recommend integrating your QuickBooks to a third-party application.
Since business needs and structures vary, we don't provide recommendations on which one to use. However, you can visit the Marketplace to get a wide range of options for compatible third-party applications.
To narrow your search, browse the apps per category, or just enter a keyword in the search field. You should now be able to find one that suits your business needs.
If there's anything else I can help you with, reach out to me by posting a comment below. I'm always here to assist you further. Wishing you the best.