I believe they mean shift-cmd-c and it copies the current URL to the clipboard. Comparable to cmd-L + cmd-C in one keystroke.

Thanks!

(Not a user of the browser in question)

But Cmd+L+C is exactly the same number of sequential keypresses as Cmd+Shift+C. So I guess Firefox has this desirable behaviour covered!

With the caveat that it changes where the cursor is.

Also it requires both hands