How to migrate "rowGroupRenderer" from previous versions to the latest?

I want render table with grouping by property in row, but i don't want add this property to columns. We show a special group-row with info about 'group by' property before grouped rows. Now it's impossible and it was main feature for using react-data-grid in our project.

If possible, can you add again this feature or make an example how we can do this in current version, please?