2026 answer.

With new power bi project file format. (If you save your pbix file to pibp)
Your power bi file now is distributed into parts.

Go to folder: ?your_power_bi_file_name?.SemanticModel/defintion/tables, and you will find all the tmdl files. These are your table definitions. Open a file and you will able to find each column and their `summarizeBy`

`summarizeBy = .....(count, sum, ect...)` this is the attribute that you want to update.

The trick here is how to change them all at once. I am able to do this via Search and replace all with help of regular expression on in vs code.

Just open the folder in vs code, and find and replace this from

 `summarizeBy = count` --> `summarizeBy = none`

In Search with regex* (make sure highlighted/on where red arrow is pointing at)

find them all using --> summarizeBy:\s*(Sum|Average|Count|Min|Max|DistinctCount)

replace with string --> summarizeBy : none

** You might need to re-open your powerbi file to take effect. **

Bonus: why not as your AI to replace it all for you.