Use the Process Aggregation capability to set the process groups to focus on and aggregate the results.
To start, go to Advanced > Process Aggregation.
You can find the processes that are present in the trace file, but not in the process group, in the Other group. By default, the data for the Other group is not displayed. To view data for the Other group, select Advanced > Show Process Group 'Other'.
To revert to the default aggregation of all processes, select Advanced > Default Aggregation.