I've got you covered, @JKMatsko. Yes, you can reassign an existing customer as a sub-customer under a different parent to help you better organize your customer hierarchy. We can do this by adding the Job of: column in the Add/Edit Multiple List Entries page.
- Navigate to the Customers Center.
- Locate the customer name you want to change and right-click on it.
- Choose Add/Edit Multiple Customer:Jobs.
- Click the Customize Columns button.
- In the Available Columns section, select Job of:, then Add.
- Move the Job of: item below the Name by pressing Move Up continuously, then Ok.
- Find the customer you want to alter and pick the new parent customer in the Job Of: column.
- Hit Save Changes.

If you have other questions in mind, feel free to Reply below. I'll be delighted to answer them for you.