If you need put popup ever on top in studio, put this css on theme raiz... 

.popup-backdrop {

    -servicestudio-position: relative;

}

Options

• PlaceHolder Title: Popup Title
• PlaceHolder Icon: Icon to close popup
• PlaceHolder Content: Popup main content
• PlaceHolder Action: Buttons and actions if you need to use the scroll layout
• ScrollHeight: Projected height for a popup scroll use max 80
• Event Close: Event to close popup