In QuickBooks Online (QBO), you can set a discounted labor rate per customer by creating tailored product/service items and adjusting pricing manually when creating invoices.
- Go to Sales and select Products and Services.
- Click on New, and then Service.
- Specify the account where you want to track the discount in the Income account dropdown.
- Hit Save.

Once done, create an invoice so that you can apply the discount.
- Tick the + New button and select Invoice.
- Choose the customer who will receive the discount.
- In the first line under Product/Services, enter the Service, Rate, and Amount.
- In the second line, select the discount you created earlier. Enter the amount as a negative value to reflect the discount accurately.
- Press Save and close to complete the process.

However, if you want to apply discounts to all your customers, you can create price rules in QuickBooks Online.
I look forward to hearing updates from you. Please let us know if you have any further questions about adjusting your customers' rates. We're always here to help.