Xcode Custom Shortcut

edit file "/Applications/Xcode.app/Contents/Frameworks/IDEKit.framework/Resources"

add

    <key>Custom ShortCut</key>
    <dict>
        <key>Duplicate Line</key>
        <string>selectLine:, copy:, moveToEndOfLine:, insertNewline:, paste:, deleteBackward:</string>
        <key>Cut Line</key>
        <string>selectLine:, copy:, moveToEndOfLine:, deleteToBeginningOfLine:, deleteBackward:</string>
    </dict>