An example of how you can get other component every where with afterburner.fx.

ViewHelper

@AllArgsConstructor
public enum ViewHelper {
    START(new StartView()),
    CHILD(new ChildView());

    public FXMLView view;
}

Controller - Main

public class StartPresenter implements Initializable {
    @FXML
    private Label label;

    @FXML
    private void clicked() {
        label.setText(((ChildPresenter) ViewHelper.CHILD.view.getPresenter()).textfield.getText());
    }

    @Override
    public void initialize(URL location, ResourceBundle resources) {
        new ChildPlace().start();
    }
}

Controller - Child

public class ChildPresenter {
    @FXML
    public TextField textfield;
}