The Scenes tool tray is missing entirely from Layout. Not anywhere. Window>Default Tray? Nope.
Using SKP 2018.
You posted this in the LayOut category. Are you indeed referring to LayOut? If so, there will be no Scenes panel in the tray. There isn’t supposed to be a Scenes panel, either. That’s a SketchUp thing. In LayOut there’s the Sketchup Model panel and in it you can choose the desired scene for a selected viewport.
BTW, your profile says you are using SketchUp 2017. Maybe you could update your profile.
Updated profile - thanks.
Staring at screen too much and bouncing between SKP /LYT to much - confused. Thanks again.