How do you segue in a mac application without creating a new window?

I'm trying to segue to the bottom view controller after hitting the submit button, but when I do it creates a new window.

Storyboard

That is one of the default behaviour of Cocoa segues. One solution is to close the previous window when moving through the segue.

override func prepare(for segue: NSStoryboardSegue, sender: Any?) {
    self.view.window?.close()
    //Pass data to new view
}

I have just found this tutorial and the developer creates a very interesting transition effect, take a look at the source code at the bottom of the page