Welcome to the Ranch.
I do not use Netbeans (nor work with JavaFX) but looks like this might answer your question https://netbeans.org/features/javafx/composer.html I will also add this question over to the IDE forums. That way you will stand a better chance of getting a more helpful answer
There used to be a JavaFX component palette in NetBeans 6.9 for JavaFX 1.3.
Additionally, the JavaFX Composer functionality of NetBeans linked by Maneesh is obsolete and not recommended.
Both JavaFX Composer and the JavaFX Palette are discontinued features and do not appear in NetBeans 7.x products.