Open the configuration From more options, enable parallel running. And then set the port for each instance. From left-top corner, duplicate the instance.
How to run a JavaFX project with Scene Builder in intelliJ
1. Check JavaFX plugin 2. Check the JavaFX project 3. Check the necessary dependencies 4. Search "javaFX" and open in preference 5. Configuration path to scenebuilder, and open scenebuilder to import FXML file