We always strive to provide the best experience with the product, HAM9.
The option to restrict the users to delete attachment is unavailable in QuickBooks Online (QBO). When setting up a user's limited access for Customers and Suppliers side they only restrict them from adding, editing, and deleting accounts and quantity on hand. However, they can create, delete statements, add, edit, and delete customers, suppliers, products, and services.
For more details about managing access and the different user types/levels of access in your account, check out these articles:
You can visit these blogs for any upcoming QuickBooks updates and enhancements:
Visit our Account management page for more insights about managing your Intuit account.
This should take you in the right direction. Keep me posted if you need a hand with running your business in QuickBooks Online. Assistance is just one click away. Have a great day.