Usually when you click on a part in flight, it will give you the temperature. Either it was intentionally removed or its just a bug. Also, the red glow of re-entry on the craft does not show up. I've tried turning on re-entry heating damage but nothing seems to work. Hoping this can be fixed in the next update :)
Re-entry visual effects must be enabled in the Settings -> Quality -> Image Effects.
Also, after enabling Re-Entry Heat Damage and/or Re-Entry visual effects, you will need to restart the flight scene for the temperature property to become visible in the part's flight inspector.