Just installed Merlin into Chrome on a new Windows 10 install. (I'm a Mac-only user by the way, just helped to a friend). Hit Ctrl-M, and it talked about Cmd-M, see the screenshot.

I had to go into the settings, Shortcuts. There was no Cmd-M, only Ctrl-M and Ctrl-Alt-M (or Shift? maybe – I'm back on my Mac). I had to clear the Ctrl-M part and change the other hotkey to Ctrl-M. Now the Siderbar worked.

This makes the plugin completely useless on Windows for the average user.