Extending JavaFX components which don't extend Node cannot be imported as a user library.

For example, create a simle class that extends TableColumn, put it in a JAR, and import it. The class is properly loaded, but the JAR analyzer complains that it doesn't extend Node (and it doesn't: TableColumn extends TableColumnBase which implements EventTarget and Styleable). Looking at the source code for SceneBuilder, it seems there are checks that weed out anything that doesn't extend Node.

SceneBuilder understands how to draw a normal TableColumn, so it seems that the application should be able to import extensions of this class.