To switch off carcass panels, follow these steps:
Select the modular unit, and navigate to the properties panel under the Cabinet section
Open the Construction icon.
Open the Carcass dropdown menu
In Carcass Visibility, there will be toggles against the different carcass panels like 'Back', 'Bottom', 'Right', etc.
Click on the toggle against any of the panels to switch off its visibility.
Click on it again to switch on its visibility.