Matrix - Can Primary Row Be It's Own Calculation From Sub-Rows?

Hi BBlue20025 

The Customize totals option works when the visual contains aggregated fields, measures, or visual calculations.

To access it, you can:

->Right click on the column that contains the Total value and select New visual calculation -> Custom
-> Or right click directly on the total cell value in the column to configure Customize totals from there.

You can also access the same option from the Build section by clicking the dropdown next to the measure or aggregation used in the table visual.

This feature was introduced starting from the March Desktop release. So if you are using an older version of Power BI Desktop, please update to the latest version to access this functionality.

For Reference;

Power BI March 2026 Feature Summary - Microsoft Fabric Community

Create and Format Table Visualizations in Power BI - Power BI | Microsoft Learn

Hope this helps. Please reach out for further assistance.
Thank you.