You can write extensions for various parts of the tool.
There is a simple way to extend your Jubula ITE to add support for a previously unsupported component on a graphics component level, e.g. if you only want to execute a click on that component. All you have to do is to add "SimpleExtensions" as a key to the property map of an AUT and a comma-separated list of fully qualified classnames as the value (Section 3.7, “Defining applications under test (AUTs)”).
Such a component has to meet some requirements depending on its toolkit.
For the JavaFX-toolkit the component has to extend javafx.scene.Node.
For the Swing-toolkit the component has to extend javax.swing.JComponent.
For the SWT-toolkit the component has to extend org.eclipse.swt.widgets.Control.
For information on how to implement a more extensive extension and all possibilities for what can be extended, see the Developer Manual.