To open a project in the current frame closing the current one:

Example: %openProject C:\Users\username\intellij


To open a project in a new frame and don't close the current one:

Example: %openProject C:\Users\username\intellij false

If you do the following: %openProject /tmp/a false %openProject /tmp/b false %openProject /tmp/a false In the end, the same project a will be active and there will be 2 window frames.
To perform Project Leak detection, pass the fourth argument as true. %openProject /tmp/a true true