In karabiner, how do I set left option to \?
&lt;?xml version="1.0"?&gt;
&lt;root&gt;
  &lt;item&gt;
    &lt;name&gt;L⌥→\&amp;L⌘→/&amp;R⌘→|&lt;/name&gt;
    &lt;identifier&gt;alttobackslashcmdtoslashandpipe&lt;/identifier&gt;
    &lt;autogen&gt;
      __KeyToKey__
      KeyCode::OPTION_L | ModifierFlag::NONE,
      KeyCode::BACKSLASH
    &lt;/autogen&gt;
    &lt;autogen&gt;
      __KeyToKey__
      KeyCode::COMMAND_L | ModifierFlag::NONE,
      KeyCode::SLASH
    &lt;/autogen&gt;
    &lt;autogen&gt;
      __KeyToKey__
      KeyCode::COMMAND_R | ModifierFlag::NONE,
      KeyCode::BACKSLASH | ModifierFlag::SHIFT
    &lt;/autogen&gt;
  &lt;/item&gt;
&lt;/root&gt;


This might not have quite the effect you want, but it's as close as I know how to do.