Extending : Reference sample : How to extend a global function to manipulate collection data : Register global function definition
  
Register global function definition
1 Open the plugin.xml and then move to the ‘Extension’ tab.
2 Click button ‘Add’ This graphic is described in the surrounding text.and input ‘global’ as a filter key to find the extension point.
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3 Move to the details panel to configure the related attributes:
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See also
How to extend a global function to manipulate collection data