The JavaFX Scene Builder Scene Builder works with the JavaFX ecosystem.
Simple Drag & Drop user interface design allows for rapid iteration.
Separation of design and logic files allows for team members to
quickly and easily focus on their specific layer of application
development.

If the font in the GUI is too small, you can open the JAR file
/opt/scenebuilder/lib/app/scenebuilder-X.Y.Z-all.jar
and edit the file 
com/oracle/javafx/scenebuilder/kit/css/Base.css
adding this line 
.root{ -fx-font-family: "Lato"; -fx-font-size: 16pt ; }
where the font and size values are the preferred ones.