Location of the default Demo Set

You can find the default demo Live Set that appears when Live first launches here:

macOS
From the Applications folder, right-click or CTRL + click on the Live application and select "Show Package Contents." Open the folder "Contents" to reveal this path:
Contents/App Resources/Core Library/Lessons/Demo Songs

Windows
C:\ProgramData\Ableton\[Live Version]\Resources\Core Library\Lessons\Demo Songs