Rename column header in visual (table)

In my table visual the column headers look like "Sum of [fieldname]"
I cannot find a way to change the text of these headers. 
Most recent solution for this is Solved: Table Visual - How can I rename the columns for a ... - Microsoft Fabric Community

but I don't see the options shown in his picture

How to solve this

I am using version 2.122.746.0 64-bit (oktober 2023)