Using the Style Property will add Inline Styling to the HTML of the listview. You cannot use selectors such as ".my-transparent-listview .mx-listview-item, .my-transparent-listview .mx-listview-item:hover" inside inline Styling.
If you want to do this, you should add your CSS to your custom stylesheet (in Studio Pro > Styling > web > main.scss) and give the listview the class .my-transparant-listview.
Or only add this code to the style property:Or only add this code to the style property:
background-color: transparent !important; border-color: transparent !important;
You can read about the difference between Inline styling (using the Style property in Mendix) and external CSS (the main.scss file) on here. And Mendix doc can be found here.And Mendix doc can be found here.