Most application developers will file a bug at http://bugs.java.com/. After checking that your bug hasn't already been reported, you can click on the “here” link on that page to go to the bug submission form. Choose “JavaFX” as the Product/Category and then select the appropriate Subcategory, Release, and Operating System.
Filing a Bug
Most of this section applies whether you enter a bug via bugs.java.com or directly in JBS.