Assuming you are running the Native Kiosk and not the Activity Suppression then as far as I am aware only way to show the app switcher is if the device is on Android 9 or higher. This is actually a function of Android Enterprise and not MobiControl specifically since the Native Kiosk is an Android Enterprise feature and each recent version of android has added new configurability. Android 9 added new Android Enterprise Kiosk controls and SOTI has simply exposed the configuration of those options within the Kiosk Profile. Unfortunately for your situation the TC56 is an Atlas family device which has likely seen its last dessert flavor upgrade, meaning you are stuck on Android 8.1. I wish I had better news for you. You could maybe explore using Enterprise Home Screen for lockdown instead of the Native Kiosk to see if that offers the controls you're looking for.