Added a custom script for still quick adding soft shadows for UI
All you need to do is drag the script to the object to which you add a shadow and click create a shadow! shadow completely customizable, color, size and 5 kinds of magnification!
Asset provides a set of soft shadows for UI.
All out on prefabs, you can make a shadow for round objects and for cube and so on.
You can change the color, opacity, size of the shadow,more detail you can see in the video.