The 'Apps' key (between right Alt and Ctrl) gives you the context menu, but it wont toggle the *§$%* thing. So you have to use your mouse to click elsewhere if you raise the menu by mistake;
I use the Esc key
forgot about that option when posting
FWIW, the history:
I'm left-handed and am usually drawing with the mouse and trying to hit a Ctrl+Otherkey shortcut and I catch the corner of the apps key - then, using the keyboard, I would have to leave the mouse to hit escape, or hit it with my right hand, both of which are a pain, especially if it keeps happening.
For a long time I had the apps key 'converted' to the Control key but I missed it in other software - actually that was how I came across dc, trying to find out how to do that.