I am using arctic white subtheme and Weaver Xtreme.
The Widget Short Code box is missing on the Widgets, as is the misc widget area where I can create
a widget just for the sole purpose of getting the shortcode.
I did add an extra widget area by defining one here: Define Per Page Extra Widget Areas so I had this
workaround, but it sure was handy to just get the shortcode at the bottom of the Widget after you saved it.
I use it all the time for x plus flex columns.