Steps:

1.Select the resource Gantt chart.
2.If the resource Gantt chart is currently not displayed, display by selecting [Window] – [New Resource Gantt Chart] from the main menu.
3.Hold down the Shift key and select the target cells to which the bars you want to drill down are assigned. The selected cells will be highlighted.
4.Right-click on one of the selected cells and select [Drilldown] from the popup menu. Tasks of the operations in the selected cells will be displayed individually in separate rows.

To close the drilldown display, click [-] to the left of the name of the resource. When you display the popup menu, you need to right-click on a portion of the cell to which the bar is not assigned.