Shortcuts for code snippets
No, while the XML schema contains a shortcut element, the fact is that proper shortcut support was never implemented (several of the other elements are not visible outside the XML, either). The following Connect item was closed as "Won't Fix" back in 2013:


Connect #731728 : SQL Server Management Studio 2012 code snippet shortcut


You may be able to raise awareness of this issue on another place where the SSMS team is paying attention: trello. But I'll warn you: even with an accelerated dev and release cycle, they have a lot on their plates, and I'm not sure this could make any significant dent into the top, say, 50 enhancements.

(Personally, I haven't found that I've need to use my mouse to insert snippets - all that is needed is keystrokes. Obviously YMMV.)