At this time, there isn't an option to edit the purchase order template. You can manually a custom field instead.
But don't worry, I'll pass along your request to our product developers so they'll know of your need to edit the purchase order template.
For updates, visit the following links below for reference:
Keep me posted in the comments if you have any other questions.
Hi there, @Rhanford.
Our QuickBooks team strives to provide excellent customer service and deliver customer satisfaction at all times. I want you to know that we value your feedback, and it would be a big help to improve the service and your QuickBooks experience.
I definitely understand how important for your business to have this feature. For now, the option to edit a purchase order template is still unavailable in QuickBooks Online.
Please know that added features in the program are based on the number of requests sent by our users. The more request they'll get the better chances it will be included in future updates.
I'll also pass this suggestion to our developers to improve your experience in QuickBooks.
In the meantime, I'd recommend following the suggested workaround that was shared by my colleague JonpriL. That way, you'll have other options in customizing the form.
It's important that we always meet our customer's needs. While we continue to make improvements, I want you to be updated with the latest QuickBooks news and product release through our Firm of the Future site. This is where we share recent happenings and future developments, such as updates to newly added features.
In case you need related resources while working with QuickBooks, please feel free to skim through the topics from our help articles.
Please let me know how else I can help you with QuickBooks. I've got your back and am always happy to help. Keep safe!