General Improvements: Provide a visual indication of the current "Variant" and "Event" being edited

On the Variant and Event subpages, the page initially starts off very blank. Once you click "Add a variant" or "Add an event" you start creating a list of items on the panel on the left, and their default name is always the same. When you select one to start editing, there is no visual indication of the current selection.

Small adjustments I'd like to propose that would go a long way in improving the user experience here includes:
- Adding a fallback, or empty state to the page when the list is empty. A message like "No Events created yet. Click the button to get started" is better than a blank screen.
- Add a visual indication such as a subtle background color, and an accented font color to the current/selected event or variant in the list.


Start at the Variant and Event subpages and trace the “Add a variant” and “Add an event” flows to the left-hand item list. Check how an empty list and the currently edited item are rendered; done means empty lists show a useful prompt and the selected variant or event has a clear visual indication.

Written by the indexing model from the issue text.