Show an app's context menu on Nexus 7 My Galaxy S1 (Gingerbread) has a context menu button below the lower left of the screen which brings up various extra soft-buttons. For example, in the Twitter app, I use this to pop-up an additional menu which includes a switch user soft-button.

I have recently acquired a Nexus 7 which is lovely. However, the three screen buttons are Back, Home, and Multitask[I think?] and I can't work out how to bring up the same context menus which I use to use. When I press the Multitask button in any app, I just get a list of running apps.

Have I missed something? Is there no context menu option in Jellybean? 

How do I get to the Twitter App switch user soft-button (etc)?
Connect your device with a USB cable,
activate USB debugging
issue: $ adb shell input keyevent 82


Alternative geeky answer, let's say.