Hello Caleb,
I appreciate you sharing the details of what changes you're hoping to make on your T4 slips. I know being able to customize forms is a wonderful feature in QuickBooks Desktop, so it makes sense to be looking for the same capability here.
In this case, editing T4 formats is not among the available options. The form that is generated by the program is regulated by Canada Revenue Agency formatting, including putting the last name in capital letters. The information filled out in the fields on the screen will be used to fill in the usual T4 slip that you're used to seeing. Feel free to take a look at the follow page from the CRA website to learn more about the required formatting: T4 Statement of Remuneration Paid (slip)
If there's a request you'd like to make that still fits in with the CRA requirements, feel free to leave feedback for us by going to the Help menu and choosing Send Feedback Online. Keep in mind that government regulations are a large factor in QuickBooks' set up, which is done to make sure you're submitted information with the correct formatting to the government.
Let me know if you have more questions!