I have been working on a software since a while in Java, and started the designing phase of it. I use JavaFX for the GUI, and use FXML for defining Scenes. I want to get the code reviewed which is related to how I handle the user interface. Like, how I render different pages, etc. Would that be considered on-topic on CodeReview?
Yes, that would be considered on-topic, often we review even css designs here.
Just make sure you include some working code and you should be fine!