This way it's more dynamic: You don't need to hardcode the plug-in name in the widget to see whether or not it's visible.
Contributes to issue CURA-6086.
They can then decide if it needs to be there. For instance, the monitor stage doesn't want to have this panel. Also each stage can position it where they like, and in the near future I'll make a feature to let it decide whether or not to show the preview button.
Contributes to issue CURA-6086.