Good afternoon, @t19671.
QuickBooks Online (QBO) should allow multiple users to work simultaneously at the same time with the different work stations. Though, the only shortcoming will be if the users edit the same existing transaction at the same time. (Working in different parts of QBO will work, but may not update properly if doing payroll at the same time)
Also, each user may need to refresh to see immediate entries by others.
You can check out this article to know more about the types of users you can add and what they can do in QuickBooks: User types and user permissions in QuickBooks.
If you have any other concerns or questions, don't hesitate to reach back out. Have a great day!