Typically, double clicking a machine in the machine view opens its parameter view. Some machines may override the double click action and provide its own user interface instead. In that case, right click the machine and select "Machine Parameters".
VSTs open their user interface embedded in the parameter view, hiding the built-in Buzé-sliders. Press the circle-shaped button on the toolbar to toggle the various parameter view display modes.
The parameter view can also be opened for audio connections: right click a connection and select "Audio Connection Parameters".