How & Where to logout
It's in a drop-down menu on the right hand side of the screen. I'd seen a screenshot of it but had not yet located... I looked everywhere!! (was attempting due diligence to follow the advice to logout and login with posting key instead of master key).
Then finally [gasp], I found it by accident when I clicked my mouse on the blank space between the "POST" button and the [3 horizontal lines] right top corner menu.
Just like a heretofore invisible faerie, a white drop-down menu appears out of nowhere.... Voila!
@griffindeva @monicamcguire [in case you are having the same issue].
Pic: Brian Froud Upside down faerie (looked everywhere!)