Hi there, SamQree.
Thanks for bringing your question forward here in the Community. I'm happy to provide some info about customizing customer forms in your QuickBooks Desktop account.
While there are many ways to customize forms in the Desktop platform, including creating custom fields, there isn't currently a way to customize forms for new customers. In this instance, I recommend submitting feedback to the Product Development Team to let them know you'd like to have this ability. This can be done directly through your account by selecting the Help tab in the top menu, then select Send Feedback Online.
I'm only a comment or post away if you have any other questions. Take care!