How to specify the form list in Qt's custom wizard of Qt Creator?

[Sammer]

Hi, guys! Recently, i am developing a plugin for Qt Creator. Specifically, I have made a custom dialog for "New File...". And I wanna insert it into the "New File" wizard of Qt Creator. I have create a wizard.json for this. I wish the list could display my custom dialog instead of the built-in ones from Qt.

Now i have read the document:
https://doc.qt.io/qtcreator/creator-project-wizards.html#:~:text=The page sets-,FormContents,-to an array
But I am confused:
What's the FormContents? Is that the variable controling list? And how can i edit this variable? Any example please?