Specify Custom CSS Properties

To specify custom CSS properties, follow these steps:

Create a file named CustomProperties.xml that has the following structure:

<?xml version="1.0" encoding="UTF-8"?>
<css_keywords
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   
      xsi:schemaLocation="http://www.oxygenxml.com/ns/css
 http://www.oxygenxml.com/ns/css/CssProperties.xsd"   
      xmlns="http://www.oxygenxml.com/ns/css">
      <property name="custom">
      <summary>Description for custom property.</summary>
        <value name="customValue"/>
        <value name="anotherCustomValue"/>
      </property>
</css_keywords>

Go to your desktop and create the builtin/css-validator/ folder structure.
Press and hold Shift and right-click anywhere on your desktop. From the contextual menu, select Open Command Window Here.
In the command line, run the jar cvf custom_props.jar builtin/ command.
The custom_props.jar file is created.
Go to [OXYGEN_INSTALL_DIR]/lib and create the endorsed folder. Copy the custom_props.jar file to [OXYGEN_INSTALL_DIR]/lib/endorsed.