The order that TestSuites are added to the project is the order they are run in, especially when executing them under the Coverage tab for the project. This is a major problem (I had to edit the XML file directly!) because of inter-dependencies between each TestSuite.
you are correct, there is no way to currently reorder TestSuites. We are working on a "TestScenario" concept which will allow you to specify which test-items to run and in which order..
