On some iOS devices, there is not an intuitive way to bring up the app carousel during a manual real device test. Below is a good, consistent way to bring up the app carousel. Please check the attached video for a walkthrough.
To get this to consistently work, go to:
> Enable AssistiveTouch
Go to your home screen via the button in the right hand pane in TestObject
Tap the grey circle, shown below:
Tap "App Switcher"
See the carousel and swipe up to close the desired app.
This is a long workaround indeed but it's consistently working on newer iOS devices without a home button.