Conditional Grouping
The Group Filter element has an Include Condition attribute.
If the value of this attribute is left blank or contains a formula that evaluates to True, the element is applied to the datalayer. If the value evaluates to False, the element is ignored and does not affect the datalayer. This powerful feature allows you to dynamically determine if the data will be grouped or not.
More than one group filter can be put under any level, specified by the attribute "IncludeCondition" for each group filter. For example, @Request.GroupColumn~ = 'City' or IncludeCondition =@Request.GroupColumn~ = 'Sales'. Once the Report is run without an error, there will be different grouping based on the given token value 'City' or 'Sales'.
In this case, the token value set in the parameters was 'City' grouping the filter by City: