import javafx.application.Application;
import javafx.geometry.Side;
import javafx.scene.Scene;
import javafx.scene.control.Tab;
import javafx.scene.control.TabPane;
import javafx.scene.layout.Priority;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class Test extends  Application {

    @Override
    public void start(Stage primaryStage) {

        var tabPane = new TabPane();
        tabPane.setSide(Side.RIGHT);

        for (var i = 0; i < 20; i++) {
            var tab = new Tab("Test " + i);
            tabPane.getTabs().add(tab);
        }
        VBox.setVgrow(tabPane, Priority.ALWAYS);
        var root = new VBox(tabPane);
        Scene scene = new Scene(root, 500, 300);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}