The attached project (4.2MB because it includes the jfxrt.jar) lets you create pure Swing windows and embedded JavaFX windows (FX). Using the NetBeans Platform window system's drag and drop lets you move windows to new locations. Always works with pure Swing windows, but fails with JavaFX (JFXPanel) windows with the following error.
SEVERE [global]
java.lang.AssertionError
at javafx.embed.swing.SwingDnD.endDnD(SwingDnD.java:325)
at javafx.embed.swing.SwingDnD.access$900(SwingDnD.java:71)
at javafx.embed.swing.SwingDnD$3.dragExit(SwingDnD.java:161)
at java.awt.dnd.DropTarget.dragExit(DropTarget.java:426)
at sun.awt.dnd.SunDropTargetContextPeer.processExitMessage(SunDropTargetContextPeer.java:401)
at sun.awt.dnd.SunDropTargetContextPeer$EventDispatcher.dispatchExitEvent(SunDropTargetContextPeer.java:838)
at sun.awt.dnd.SunDropTargetContextPeer$EventDispatcher.dispatchEvent(SunDropTargetContextPeer.java:772)
at sun.awt.dnd.SunDropTargetEvent.dispatch(SunDropTargetEvent.java:48)
at java.awt.Component.dispatchEventImpl(Component.java:4716)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.trackMouseEnterExit(Container.java:4612)
at java.awt.LightweightDispatcher.processDropTargetEvent(Container.java:4558)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4417)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:713)
at java.awt.EventQueue.access$000(EventQueue.java:104)
at java.awt.EventQueue$3.run(EventQueue.java:672)
at java.awt.EventQueue$3.run(EventQueue.java:670)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:686)
at java.awt.EventQueue$4.run(EventQueue.java:684)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:683)
at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:158)
[catch] at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)