I'm writing new release DigLayout v.3 Layout Manager for JavaFX. In version 3 you can resize object in runtime and DigLayout intercept all change and resize your layout using your roules. DigLayout 3 support: horizontal and vertical alignment, horizontal and vertical gap and colspan. You can insert, delete, change, resize,... Nodes in DigLayout at run time.
I'm also writing a JavaFX visual tool for write graphic interfaces (with advanced support of DigLayout 3) than you can draw a new interface without source code. My tool generate all graphic interface JavaFX source code that you can use in your application.