The task manager should detect an existing session. If the task manager is already running, launching a new instance should result NOT in opening a 2nd instance, but in bringing up and focusing the existing instance. 

With 1.0.0 I often fall in the following pattern: open xfce4-taskmanager, close the instance using the WM which results in the instance minimizing to systray, then later I forget that an instance is already running and launch xfce4-taskmanager again. At this point a 2nd instance opens and thus a 2nd icon in the systray. I believe this is unnecessary. In such a case best would be to detect a running instance and simply switch to it.