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>