By default, the MultiRow control creates column headers that span multiple rows and shows the header for each cell defined in the layoutDefinition.
These cell-specific column headers may be used to sort or filter the data as you would do in a conventional grid.
In some cases, you may want to collapse the column headers to a single line, showing only the group names rather than individual cells. This saves space at the expense of having individual cell headers. To collapse the column headers, set the collapsedHeaders property to true. In these scenarios, remember to set the header property on the groups in order to avoid empty column headers.