Solution
Use a TextFlow (Java 8):
TextFlow flow = new TextFlow(
new Text("Don't have an account? "), new Hyperlink("Click here")
);
Use a FlowPane (Java 7):
FlowPane flow = new FlowPane();
flow.getChildren().addAll(
new Text("Don't have an account? "), new Hyperlink("Click here")
);
Sample
Here is a complete, executable example (Java 8):

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.text.*;
import javafx.stage.Modality;
import javafx.stage.*;
public class TextLink extends Application {
@Override
public void start(final Stage primaryStage) throws Exception {
Stage accountCreation = buildAccountCreationStage(primaryStage);
Hyperlink createAccount = buildCreateAccountLink(primaryStage, accountCreation);
TextFlow flow = new TextFlow(
new Text("Don't have an account? "), createAccount
);
flow.setPadding(new Insets(10));
primaryStage.setScene(new Scene(new Group(flow)));
primaryStage.show();
}
private Hyperlink buildCreateAccountLink(Stage primaryStage, Stage accountCreation) {
Hyperlink createAccount = new Hyperlink("Click here");
createAccount.setOnAction(event -> {
accountCreation.setX(primaryStage.getX());
accountCreation.setY(primaryStage.getY() + primaryStage.getHeight());
accountCreation.show();
});
return createAccount;
}
private Stage buildAccountCreationStage(Stage primaryStage) {
Stage accountCreation = new Stage(StageStyle.UTILITY);
accountCreation.initModality(Modality.WINDOW_MODAL);
accountCreation.initOwner(primaryStage);
accountCreation.setTitle("Create Account");
accountCreation.setScene(new Scene(new Label("<Account Creation Form Goes Here>"), 250, 50));
return accountCreation;
}
public static void main(String[] args) { launch(args); }
}
The default link highlight is kind of strange with the dashed border around it (if you wish you can style it with css to get something nicer and more similar to links on the web; i.e. just different colored text to indicate visited and unvisited links).
Aside
For you particular message, you should just make the "Don't have an account" text a hyperlink and get rid of the "Click here" text (as recommended by the w3c web standards body).
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