Dynamic headers for a balance sheet

Mpmp1​ 

I believe "fabric model" you mean a semantic model in Direct lake storage mode. If so then create calculated columns or custom tables in direct lake storage mode. As long as you are using direct lake on one lake, please refer the below blog

Direct Lake Calculated Columns (Preview) | Microsoft Fabric Community

If you are using direct lake on sql, then for custom column or custom table you can directly create them with your warehouse or lakehouse and use it. 

If none of the options solves your requirement and you still want to use a measure as column header then its not possible in power bi native table or matrix visual. However I created a custom visual using calude code called "Smart Table" and wrote a blog about its features, you can refer to it.

https://www.techietips.co.in/articles/powerbi-smart-table