How do I show 'Golden Hour' on the timeline?

You can configure what information is displayed in the timeline below the map by double-tapping (or long-pressing) on it:

A list of options is displayed - note that you can configure Day mode and Night mode independently. Golden Hour is included in both "Extended Daylight" and "Day Mode: All". For further details, please review the user guide within the app (also available here).

Day mode

Night mode