Hello jpilkington,
Being able to control what your users see in QuickBooks Online can be an important part of keeping certain information private or making sure it doesn't get accidentally edited. I'm happy to go over this with you.
While the program allows you to create users with access limited to supplier information, there isn't a way to limit that access further. I can appreciate certain people only needing to handle certain functions, but at this time, QuickBooks Online cannot accommodate those kinds of specificities in its user setup.
Here's more information about the user types available: Learn about user types in QuickBooks Online
I'm here if you need any clarification or have more questions. :)