Karabiner Setting (For UK mac keyboard, IntelliJ settings..)

private.xml

<?xml version="1.0"?>
<root>
  <appdef>
    <appname>IntelliJ IDEA</appname>
    <equal>com.parallels.desktop.console</equal>
    <equal>com.jetbrains.intellij.ce</equal>
  </appdef>

  <deviceproductdef>
    <productname>APPLE_INTERNAL_KEYBOARD_TRACKPAD_0x0273</productname>
    <productid>0x0273</productid>
  </deviceproductdef>

  <deviceproductdef>
    <productname>APPLE_ALUMINUM_KEYBOARD_UK_0x0250</productname>
    <productid>0x0250</productid>
  </deviceproductdef>

  <!--
      <devicevendordef>
      <vendorname>MICROSOFT</vendorname>
      <vendorid>0x045e</vendorid>
      </devicevendordef>

<deviceproductdef>
<productname>MICROSOFT_ERGONOMIC_KEYBOARD</productname>
<productid>0x00db</productid>
</deviceproductdef>
  -->
  <!--
      <item>
      <name>Swap Command and Option (IntelliJ)</name>
      <identifier>private.app_intellij_swap_command_and_option</identifier>
      <only>IntelliJ IDEA</only>
      <device_only>DeviceVendor::MICROSOFT, DeviceProduct::MICROSOFT_ERGONOMIC_KEYBOARD</device_only>
      <autogen>__KeyToKey__ KeyCode::OPTION_L, KeyCode::COMMAND_L</autogen>
      <autogen>__KeyToKey__ KeyCode::COMMAND_L, KeyCode::OPTION_L</autogen>
      <autogen>__KeyToKey__ KeyCode::COMMAND_R, KeyCode::OPTION_L</autogen>
      </item>
  -->
  <item>
    <name>UK layout For Apple Keyboards (For UK Macbook 0x0273 and Mac UK keyboard 0x0250) </name>
    <!--
    <item>
      <name>Swap Backquote and Section</name>
      <identifier>private.swap_backquote_and_section</identifier>
      <block>
        <device_only>DeviceVendor::APPLE_COMPUTER, DeviceProduct::APPLE_INTERNAL_KEYBOARD_TRACKPAD_0x0273</device_only>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, KeyCode::BACKQUOTE</autogen>
        <autogen>__KeyToKey__ KeyCode::BACKQUOTE, KeyCode::UK_SECTION</autogen>
      </block>
      <block>
        <device_only>DeviceVendor::APPLE_COMPUTER, DeviceProduct::APPLE_ALUMINUM_KEYBOARD_UK_0x0250</device_only>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, KeyCode::BACKQUOTE</autogen>
        <autogen>__KeyToKey__ KeyCode::BACKQUOTE, KeyCode::UK_SECTION</autogen>
      </block>
    </item>
    -->
    <item>
      <name>Change Fn + Section to Section</name>
      <identifier>private.uk.fn_section2section</identifier>
      <block>
        <device_only>DeviceVendor::APPLE_COMPUTER, DeviceProduct::APPLE_INTERNAL_KEYBOARD_TRACKPAD_0x0273</device_only>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, ModifierFlag::FN, KeyCode::UK_SECTION</autogen>
      </block>
      <block>
        <device_only>DeviceVendor::APPLE_COMPUTER, DeviceProduct::APPLE_ALUMINUM_KEYBOARD_UK_0x0250</device_only>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, ModifierFlag::FN, KeyCode::UK_SECTION</autogen>
      </block>
    </item>

    <item>
      <name>Change Section to Backquote (Except with FN)</name>
      <identifier>private.uk.section2backquote</identifier>
      <block>
        <device_only>DeviceVendor::APPLE_COMPUTER, DeviceProduct::APPLE_INTERNAL_KEYBOARD_TRACKPAD_0x0273</device_only>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, ModifierFlag::NONE, KeyCode::BACKQUOTE</autogen>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_SHIFT, KeyCode::BACKQUOTE, ModifierFlag::SHIFT_L</autogen>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_CONTROL, KeyCode::BACKQUOTE, ModifierFlag::CONTROL_L</autogen>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_COMMAND, KeyCode::BACKQUOTE, ModifierFlag::COMMAND_L</autogen>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_OPTION, KeyCode::BACKQUOTE, ModifierFlag::OPTION_L</autogen>
      </block>
      <block>
        <device_only>DeviceVendor::APPLE_COMPUTER, DeviceProduct::APPLE_ALUMINUM_KEYBOARD_UK_0x0250</device_only>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, ModifierFlag::NONE, KeyCode::BACKQUOTE</autogen>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_SHIFT, KeyCode::BACKQUOTE, ModifierFlag::SHIFT_L</autogen>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_CONTROL, KeyCode::BACKQUOTE, ModifierFlag::CONTROL_L</autogen>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_COMMAND, KeyCode::BACKQUOTE, ModifierFlag::COMMAND_L</autogen>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, MODIFIERFLAG_EITHER_LEFT_OR_RIGHT_OPTION, KeyCode::BACKQUOTE, ModifierFlag::OPTION_L</autogen>
      </block>
    </item>
    <item>
      <name>Change Backquote to shift (left)</name>
      <identifier>private.uk.section2shiftL</identifier>
      <block>
        <device_only>DeviceVendor::APPLE_COMPUTER, DeviceProduct::APPLE_INTERNAL_KEYBOARD_TRACKPAD_0x0273</device_only>
        <autogen>__KeyToKey__ KeyCode::BACKQUOTE, KeyCode::SHIFT_L</autogen>
      </block>
      <block>
        <device_only>DeviceVendor::APPLE_COMPUTER, DeviceProduct::APPLE_ALUMINUM_KEYBOARD_UK_0x0250</device_only>
        <autogen>__KeyToKey__ KeyCode::BACKQUOTE, KeyCode::SHIFT_L</autogen>
      </block>
    </item>
    <!--
    <item>
      <name>Change Fn + Section to Backquote</name>
      <identifier>private.uk.fn_section2backquote</identifier>
      <block>
        <device_only>DeviceVendor::APPLE_COMPUTER, DeviceProduct::APPLE_INTERNAL_KEYBOARD_TRACKPAD_0x0273</device_only>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, ModifierFlag::FN, KeyCode::BACKQUOTE</autogen>
      </block>
      <block>
        <device_only>DeviceVendor::APPLE_COMPUTER, DeviceProduct::APPLE_ALUMINUM_KEYBOARD_UK_0x0250</device_only>
        <autogen>__KeyToKey__ KeyCode::UK_SECTION, ModifierFlag::FN, KeyCode::BACKQUOTE</autogen>
      </block>
    </item>
    -->
    <!--
    <item>
      <name>Change Backquote to Section</name>
      <identifier>private.uk.backquote2section</identifier>
      <block>
        <device_only>DeviceVendor::APPLE_COMPUTER, DeviceProduct::APPLE_INTERNAL_KEYBOARD_TRACKPAD_0x0273</device_only>
        <autogen>__KeyToKey__ KeyCode::BACKQUOTE, KeyCode::UK_SECTION</autogen>
      </block>
      <block>
        <device_only>DeviceVendor::APPLE_COMPUTER, DeviceProduct::APPLE_ALUMINUM_KEYBOARD_UK_0x0250</device_only>
        <autogen>__KeyToKey__ KeyCode::BACKQUOTE, KeyCode::UK_SECTION</autogen>
      </block>
      </item>
    -->
  </item>

  <item>
    <name>Enable at only IntelliJ</name>
    <item>
      <name>Change Command_L to Option_L</name>
      <identifier>private.app_intellij_commandL2optionL</identifier>
      <only>IntelliJ IDEA</only>
      <autogen>__KeyToKey__ KeyCode::COMMAND_L, KeyCode::OPTION_L</autogen>
    </item>
    <item>
      <name>Change Command_L to Option_L</name>
      <appendix>(Pass-Through Tab and Backquote)</appendix>
      <identifier>private.app_intellij_commandL2optionL_except_tab</identifier>
      <only>IntelliJ IDEA</only>
      <include path="{{ ENV_Karabiner_Resources }}/include/checkbox/snippets/modifier_tab_to_command_tab_backquote.xml">
        <replacementdef>
          <replacementname>FROM_MODIFIER</replacementname>
          <replacementvalue>COMMAND_L</replacementvalue>
        </replacementdef>
        <replacementdef>
          <replacementname>TO_MODIFIER</replacementname>
          <replacementvalue>OPTION_L</replacementvalue>
        </replacementdef>
      </include>
    </item>
    <item>
      <name>Change Option_L to Command_L</name>
      <identifier>private.app_intellij_optionL2commandL</identifier>
      <only>IntelliJ IDEA</only>
      <autogen>__KeyToKey__ KeyCode::OPTION_L, KeyCode::COMMAND_L</autogen>
    </item>
  </item>

</root>

See How to remap keys in OSX to get the idea how to load private.xml.