I first want to say that I've been using Naninovel for over a year and I think it's great—it has exceeded my expectations. It can pretty much do everything I want my game to do. That said, I have a few of suggestions.
1.) The unlockable tips feature is great. Currently, there is an option to put in a category. I think it would be nice if that category section was functional—the tips could be organized by category and the user could click on that category.
Example: https://imgur.com/srCbUCO
Right now, I have a long list of words and I think that when the user wants to go back to read about the item again, it would be easier for them to be able to find it via a category.
2.) Right now, @input shows a field UI. Would it be possible to have a similar command with a dropdown list? This will prevent the user from writing in anything other than the intended response. It's probably easy for someone with basic C# programming knowledge to make this on their own, but I just have a very rudimentary knowledge and am not clear on how to make this.
3.) I'm not sure how feasible this would be, but would it be possible to make a character (user?) creation page? It would be a page where the user could enter his or her character's name and other information. This information can be used to customize the game more.
Example: https://imgur.com/GweRnKm