Set Gantt Chart Subproject Properties
Use the Sub-project Settings dialog to show/hide the subprojects that should be included in a Gantt chart, time-distance diagram, or mass haulage diagram, as well as to set the subproject to which new data will be added by default. All with the Active flag set are listed. The one with the Default flag is the preselected project. When you create a new Gantt chart, only one can be selected.
Ways to access
Options
Show/Hide subproject Data in Views
Selected for display - When your project contains many subprojects, check boxes in this column to show/hide just the ones you want to see in the chart.
Default subproject - Only one subproject can be checked; new Activities added are automatically assigned into this subproject.
Select All and Deselect All - When your subproject list is long, use these buttons to make selecting the needed subprojects easier.
Add - Create a new subproject.
Edit - Change the subproject settings.