Custom command on Xcode

custom-commands.plist

    <key>Customized</key>
    <dict>
        <key>Duplicate Current Line Below</key>
        <string>selectLine:, copy:, moveRight:, paste:, moveLeft:</string>
        <key>Duplicate Current Line Above</key>
        <string>selectLine:, copy:, moveToBeginningOfLine:, paste:, moveLeft:</string>
        <key>Delete Current Line</key>
        <string>selectLine:, deleteBackward:</string>
    </dict>

Custom command on Xcode.

cd /path/to/Xcode.app/Contents/Frameworks/IDEKit.framework/Resources
sudo vim IDETextKeyBindingSet.plist

In Xcode Preferences -> Key Bindings search for the names of the keys.