Hi,
The IndexNow plugin currently doesn't automatically track any change for tags or categories on any site developed with WordPress. I'm not sure if it's a bug or not a planned feature, but I believe we could benefit with automated content update in the search results. In my case I have many tags and categories being created, modified or deleted every day, and when the changes aren't at least informed to search engines (Unless I submit the affected URL' manually) I begin to question a little IndexNow usefulness when compared to traditional techniques.