By default, the "Single line mode" option is selected (ticked). The details for each of the documents in the list will display in a single line. If you select this option, a blue column header "Use your mouse to pull a column here to group on that column" will be not be displayed on which the similar data in columns can be grouped.

Single line mode selected

The details for each of the documents in the list will display in a single line.

documents-single-line-mode-selected

Single line mode not selected

If the  "Single line mode" option is not selected a blue column header "Use your mouse to pull a column here to group on that column" will be displayed and the similar data in columns will be grouped.

documents-single-line-mode-not-selected

All similar data in columns will be displayed once, e.g. Dates, Document groups, Salespersons, etc.

If you wish to retain your layout, click on the Save grid layout button.