In the HouseBuildingSample.gan file that came with ganttproject 2.8.4 (Pilsen) for Mac, I notice that some tasks have a "Project" checkbox in the task properties on the General tab, while the rest have the "Milestone" checkbox. I also notice that the tasks that have the Project checkbox (by the way, the box is there but in all cases it is unchecked in the HouseBuildingSample), there is a different type of indicator on the Gantt Chart timeline. It seems to indicate major phases of a project. I would like to learn how to create these type of "Phase" related tasks. How do I do this? I have not been able find any documentation on this? Thanks in advance.