Is there a way to create a dialog/panel to edit or request user data?
In Atom/VSCode I can create a view that is exposed in JS with the traditional DOM/HTMLElement api and tell the workspace to open it as a dialog/sidebar, etc.
I don’t think a free form input/dialog is available, but you can use NotificationRequests to get text/button clicks from users. Maybe that will work? 
I was looking to make a dialog to let the user edit entries/data.
You can pre-fill the notification dialog with a value using the textInputValue, but if that doesn’t fit what you need I’m not sure there’s anything built into Nova to support this.
Maybe you could save a file in the extension using nova.extension.globalStoragePath, add a watcher to reload the extension whenever that file is changed using nova.fs.watch(), and finally add a task that opens the file, allowing users to modify the contents?
It’ll make updating the data in the file entirely free form since users will just be modifying a text file and that opens the way for typos and other forms of input errors, but I don’t really see another way to achieve what you want