Good day, LaterWhen!
I understand that you don't need the other columns in the Sales by Product/Service Summary report. Allow me to help you in removing them.
Although we can customize the reports in QuickBooks Online, there are others that have default columns and we're unable to remove them. One of them is the Sales by Product/Service Summary report.
What you'll want to do is export the report to an Excel file. From there, you can remove the % OF SALES, AVG PRICE, and QUANTITY. Simply click the Export button next to Print, and select Export to Excel.
I included this article if you need detailed steps on how to run, customize, save reports, and learn more about report features: Run reports in QuickBooks Online.
I'd like to help you out again if you have more questions about financial reports. If you have something else to do in QuickBooks, let me know and I'll lend a hand.