Hello there, ivankomash.
Good to see you here in QuickBooks Community. Let me help and and guide you on how to customize Sales reports in QuickBooks Desktop.
You're on the right truck customizing the Sales Report. Let me walk you through on how to show only the selected customer:
- At the top menu bar, click Reports.
- Select Sales.
- Go to Sales by Customer Summary.
- Click Customize Report.
- Choose the Filters option.
- On the Search Filter tab, type-in Name.
- Select the Name drop-down arrow.
- Select your customer's name you want to show on the sales report.

For additional reference, you can check this article on how to customize customer, job, and sales reports.
If you need further assistance with the steps, I encourage you to contact our QuickBooks Desktop Support Team. They have additional tools to pull up your account and do a remote session.
Here's how to contact our phone support:
- Click this link: https://payroll.intuit.com/support/contact/?infosrc=qs&service=16.
- Select your payroll subscription.
- Choose Payroll for the topic.
- Click View Contact Info to get the phone number.
That should do it! Please know that I'm just a post away if you have any other concerns about Sales Report. Wishing you and your business continued success.