Hi Rewa,
Happy Monday and welcome to the forums!
That’s a great question. Community Events actually leaves the “Add Media” feature out intentionally because having it there would cause a WordPress security issue. The form allows specific image types to be uploaded for the Feature Events, but “Add Media” is different in that any file type could be uploaded to your server, including harmful ones. That’s the reason it was left out and why there is no setting to bring it back.
Sorry I don’t have an answer for re-displaying the button, but does this at least help answer your question? Please let me know.
Thanks!
Geoff