You cannot directly add views on a ScrollView in the Designer !
Yes, in the example I mentioned the ScrollView is added in the code, but you could also create a separate layout file with the ScrollView and load it.
To create and see the content of the ScrollView in the Designer you must define, in a separate layout file, a Panel and add all the Views on this Panel.
Then in the code you must load this layout file onto the inner ScrollView panel with ScrollView.Panel.LoadLayout("xxxx") and set the ScrollView.Panel.Height property to the height of the Panel containing the Views.
To display, in the Designer, the lower 'invisible' part of the Panel set it's Top property to a negative value.
And this is shown in the example.
Best regards.