Dash callback in a separate file

Here is a trick being used to hide multiple layouts on the same page: How to pass values between pages in dash

@chriddyp is this what you meant?

@Philippe where do you call:
app.run_server(debug=True, port=8080)?

Great answer by chriddyp. Really helped me to refactor my code. I am still struggling with some callbacks having many parameters? What is a good way to refactor those callbacks? Any link you can redirect me to?