Can’t find SCENES under WINDOWS on Sketchup Pro 2021
It is normally in the Default tray like it’s been for years.
If you aren’t seeing it, enable it under Window>Default Tray.
Please correct your forum profile. It says you are using SketchUp 2018.
It might be under Window on the Mac.
His profile says he’s using Windows.
My Mac reference was meant in case the OP had been reading the Help for the Mac version by mistake.