Showcase slider type - Dark overlay
You can create the a dark overlay effect by following the steps below.
Switch to Expert mode before proceeding.
Adding the background colorAdd a background color to the Slider settings → General tab → under Showcase slider type - Settings: Slider → CSS. E.g.
If you're running 3.3.12 or newer you can also use the Slider background color.
Add an opacity to the slides
Scroll further down the page and find the Opacity setting under Showcase slider type - Animation. Turn it on and adjust the Before and After values.