Welcome to our forum!
In Outlook, I'm afraid you can't directly see the creator who created the appointment. As an alternative, you can try adding attendees, and the creation will be displayed. Like the image below.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment". Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.