How to switch Karabiner profile via shortcut?
Yes, there is, using Karabiner's command-line tool. Paste this into your private.xml:

&lt;vkopenurldef&gt;
    &lt;name&gt;KeyCode::VK_OPEN_URL_SHELL_switchprofile_newitem&lt;/name&gt;
    &lt;url type="shell"&gt;
        &lt;![CDATA[    /Applications/Karabiner.app/Contents/Library/bin/karabiner select_by_name NewItem    ]]&gt;
    &lt;/url&gt;
&lt;/vkopenurldef&gt;
&lt;item&gt;
    &lt;name&gt;Switch Profile to NewItem with F4&lt;/name&gt;
    &lt;identifier&gt;private.switch1&lt;/identifier&gt;
    &lt;autogen&gt;
        __KeyToKey__
        KeyCode::F4,
        KeyCode::VK_OPEN_URL_SHELL_switchprofile_newitem
    &lt;/autogen&gt;
&lt;/item&gt;


Obviously, you will need to change the name of the profile (here it is NewItem).

If you want to toggle between them with a single hotkey, paste it twice and change the name, then check the box for the profile you want to switch to on each one.