Thanks for joining this thread, Pegasus23.

If you're referring to your Sales by Customer Detail report mentioned in KlentB's post, there's a couple different ways you can customize and filter it by specific customers.

Here's how to filter a report by customer in the new enhanced experience:
 

1. Run your report from the Reports screen.
2. Use your Filter option.
3. In the Filter by drop-down list, choose Customer.
4. From your Options drop-down, pick an appropriate option.
5. Using the Value drop-down, specify which customers you do/don't want to appear on your report.
6. When you're finished, select the X (Close) option on your Filter screen.
   
   

You can also use the Switch to classic view on some customer-based reports, and customize it that way:
 

1. While the report's pulled up, click its Switch to classic view button, then Customize.
2. Find your Filter section and expand it, then tick the Customer checkbox and use drop-down list to specify which customers you want to appear on your report and select Run report.
   
   

I've also included a detailed resource about customizing reports which may come in handy moving forward: Customize reports

Please don't hesitate to send a reply if there's any additional questions. Have a great Friday!