Hi nickf1,
Thank you so much for your post and my apologies for the late response. To do this, I would recommend to export the report to Excel and make the changes there. You can also visit this help articles for more information about: Exporting reports and Saving and deleting custom reports
You can also contribute your support here to potentially include this feature in our future updates: Product Ideas
Reports: Ability to create own report
Feel free to post again if you have further queries and one of us will be happy to assist you.
Regards,
Earl