[JKT]

You can already copy the "Tab" that has focus by clicking it and pressing command-C. When you paste in other apps, you will get the URL (though, by extension, dragging and dropping should also work as well as it is the Macintosh way™).

FWIW, to have a "Copy URL of Tab" in the contextual menu that I requested would be so that you don't have to first give that tab focus (so you can copy the URL of any tab, rather than the one you are currently working on).