I might be missing something but I have yet to find the GUI option to add a box shadow or drop shadow.
There is no GUI option for settings Box-shadow and certain other CSS properties, but you can do two things to get your styling added
select element and they It’s Style Property in Prop panel you can add you box-shadow
you select your element then in CSS tab next to every CSS name there is an icon </> you can click on it and edit the styling you need just like anyother editor.
press ctrl+e(pc) or cmd+e (mac) will open code window now from top of code window you can switch between CSS/HTML and can add your css
try this…css shadow tutorial