Being able to assign multiple worker's comp codes to your employees is a good idea for managing your business, Hc. I'll provide two scenarios below to help you address your concern.

If you used QuickBooks Desktop before and switched to QuickBooks Online (QBO), please note that they are separate platforms and so have different features. In QuickBooks Desktop it's possible to assign worker's comp inside the employee information. I'll show you how:

1. Go to the Employee Center, then select the specific employee you want to assign. 
   
     
2. Click the Pencil icon on the upper right. 

    

   
3. Choose Worker's Comp under Employment Info.  

    

   
4. Hit the Dropdown and add the code.
5. Select OK.

On the other hand, if you're not using QuickBooks Desktop, may I know what QuickBooks product you use? In QuickBooks Online, assigning multiple employee worker's comps is not available.

Additionally, this article helps you learn how to edit the rate for a worker's compensation code in QuickBooks Desktop: Set up manual Workers' Compensation in QuickBooks Desktop.

If you have any other questions or want to address your concern regarding worker's compensation, get back to this thread and we're here to help you.