Hello, @ks4711.
Thank you for providing details of your concern. In QuickBooks Desktop you can only assign one workers' compensation code to each employee, based on their main line of work. Also, you have the option to change the code for each of them but you can only use one.
To learn more, please see this article: Workers’ Compensation.
For your future reference, you may visit this link: Workers' Comp Class. This article will provide you steps in assigning workers' compensation classes to your employees.
Don't hesitate to update me as to how things go. I'm still be here if you need anything else. Have a good one.