Welcome to the QuickBooks Community forum. I see you have concerns with Garnishments in QuickBooks Online. I'm here to share information and guidelines to help you with this.

Yes, you can set up more garnishments for your employee even if he already had one. Here's how:

1. Go to Payroll, then Employees.
2. Select your employee.
3. From Deductions & contributions, pick Start or Edit.
4. Choose + Add Garnishment.
5. In the dropdown menu ▼select the Garnishment Type.
6. Enter a description. This will show on your reports and pay stubs. It's a good idea to enter both the employee and agency names so that you’ll recognize which agency is owed the garnishment. 
7. Enter the following fields based on the garnishment type you chose.
8. Click Save.
9. If your employee has multiple garnishments, select the dropdown menu ▼ next to Garnishment weighting to select the order in which the garnishments are collected.
10. Choose Done.

For detailed information, refer to this article: Set up and collect garnishments.

I'm adding these articles you can use in the future:

• Set up and pay an owner's draw.
• Set up and manage payroll schedules.

This information and guidelines I shared should help set up more garnishments for your employees. If you have any more questions or concerns, don't hesitate to ask. Have a great day!