You're unable to edit the dropdown (for example, Main Email) options under the Customer Information, @PremierRef2019. I'll gladly share more details about this below.

For the time being, editing the general/default data fields, like Main Email, isn't an option in QuickBooks Desktop (QBDT). However, you can create custom fields to capture specific customer details. You can learn more on how to do this by checking out this article: Create and use custom fields in QuickBooks Desktop.

Also, you may want to check out one of our Help pages as your guide in managing your company's income and customers in QBDT: Sales and customers help for QuickBooks Desktop. It includes topics about sales transactions, processing payments, and customizing forms, to name a few.

I'm all ears if you have other concerns about managing customers' data in QBDT. You can drop a comment below, and I'll gladly help. Take care always, @PremierRef2019.