When you create a new document, you can choose the MicroStrategy report to be the grouping and sorting dataset for the document. The document can be grouped and sorted using fields from the primary dataset only.
The grouping and sorting dataset is bold in the Dataset Objects panel.
When you change the grouping and sorting dataset of a document, all the grouping fields that are associated with the old grouping and sorting dataset but do not exist in the new one are removed. These items are also removed from the corresponding headers and footers.
Open a document in Design or Editable Mode.
In the Dataset Objects panel, right-click the dataset that you want to be the primary dataset and select Set as grouping and sorting Dataset. The dataset appears in bold text.