In Column Options, you set the number of columns that should be showing in the Data Grid by default. Also specify the column width of each available columns. 1 from Tasks and Hierarchy, and all fields added to Additional Columns.

By default only 1 column is showing. The others can be displayed by using the scrollbar in the Data Grid, or by dragging the Separator Line. Dragging the line will only be a temporary change.

Options:

Based on these fields:

3 columns showing, with column widths set individually: