Hey there, @gary-dr-wu.
The option to assign two workers' comp classifications to your employee's profile is unavailable in QuickBooks Online (QBO). For now, we can only set up one worker's comp insurance per employee.
I can see how this option would be helpful to your business especially when tracking workers’ compensation insurance. Thus, I'll take note of this as a suggestion to improve your experience in the program.
For additional reference, please see this article: Understand workers’ compensation insurance.
Please let me know if you have further questions with regard to assigning worker's comp to your employees. Just add them to the thread and I'll be happy to answer them for you.