How to add border radius?
Border radius for the whole slider
Be sure to switch to Expert mode first. Then go to the Slider settings → General tab → under Simple slider type settings and locate the Border setting. Set the border radius to the value you would like to have, then write
to the Slider → CSS field.
Border radius for specific edges
In Expert mode locate the Slider settings → General tab → under Simple slider type settings → Slider: CSS. You can write here the codes to achieve the desired Border radius effect.
Don't forget to write
overflow: hidden;as well.