The shortcut Cmd+Shift+V should invoke the paste special. But as I mentioned during GSoC, there's a difference between using the menu item and the general Paste Special shortcut.
Paste Special was supposed to be an abstraction layer with several sub modules, one of them the Paste CSV as markdown. There could be x more. e.g. paste HTML as markdown
The menu item will do exactly that. It will paste the csv as markdown. There should not be a shortcut for this action directly or any other sub module.
The Cmd+Shift+V should check the clipboard for the source data and choose the most appropriate action automatically. If there's any ambiguity, a warning should be presented.