As shown here

not more than 2 fields can be added in the group by section for a report, if a user desires a different layout than a tabular format.
Example: if a user has an N number of fields in the show me section but a >3 number of fields in the group by section,… all the widgets are deactivated.
In other words, there is no (N,3) section in the above chart or (N,4) ; (N,5) etc.
The widgets should not be limited to the options in that chart.