Following your example, you would edit the event at 9 am today, change the status to "Held", add a comment indicating that they changed it to tomorrow, and then you mark the "create follow up" checkbox, set the follow-up date to tomorrow at 10 am and set the follow-up type.
What happens when you save is that a NEW event record is created copying all the details of the first event and filling in the "Related To Do" field so you can easily navigate the history. On this new event, you will get popups, notifications and any other actions you have configured in the workflow system as it is "just" another event on the calendar.