Woud be great to see typing function in the prototyping mode. It could be made by combining text boxes and components (By using states). This feature needs some advanced insights to be clearly sorted, but in live, we will use this functionality in our user test.
Thank you for sharing your feedback. As Ares suggested to share your feedback on our XD uservoice page. We would also request you to please share the feedback link over here so that we can also keep a track of it for future references.