Hey Peter,
Thanks for reaching out. We don’t quite have an HTML input like you describe, which I am sorry about 🙁
You can learn more about all of our additional-field types here: https://theeventscalendar.com/knowledgebase/pro-additional-fields/
As for getting the shortcodes to be added dynamically to events, you could do this with some custom coding but there’s unfortunately not a way of doing this with the plugins as they are “out of the box”, so to speak. I’m sorry to bear this news, but please let me know if it is helpful and/or if there is anything else I can help with.
Thank you!
George