What happens to existing entries for a project when I add, or remove a phase for a project type?
When you edit the Project Type Phase Settings for the Project Types and then save, you will be presented with a message stating the following:
"You have selected to change the phase settings for this Project type. This Project type has existing Projects with phases. Changing the phase settings for this Project type will reset these Projects to the initial phase."
This warning will only be applied if you actually change the phase type for the project type. Only adding an additional phase step will not reset your existing projects.