Show a live preview event when adjusting calendar event settings

Users want to see a sample calendar event while adjusting calendar event settings so they can immediately understand how their changes will look in practice. A preview or mock event above the settings would make it easier to fine-tune display choices without saving changes and then going back to the calendar to check the result.

Why it matters: A live preview makes calendar settings easier to understand, reduces trial and error, and helps users configure event display more confidently.