You’ll find that some tasks have several smaller components that need to be tracked. However, these tasks usually aren’t large enough to require another project file. You can, however, make these tasks subtasks, so that they are connected to the main task. The main task’s duration will reflect all the subtasks.

First, make sure your tasks are in the list and that they are underneath the main task.

Then, use the Indent button on the formatting toolbar to move them in a level.

You can see how Task #25 has a black bar in the Gantt chart, and has a minus sign in the task listing.

Note, too, that you can create many levels of tasks.