Implement a Shutdown Confirmation?

One way to get a confirmation dialog upon hitting the shutdown button is to enable Shutdown Event Tracker:

Configure Shutdown Event Tracker on the Local Computer

Since the link above is not up-to-date for Windows 10, the following are step-by-step instructions for Windows 10 (verified with version 21H1):

• Start gpedit.msc
• In the Local Computer Policy navigation pane, expand Computer Configuration, expand Administrative Templates, and click All Settings
• In the console pane, scroll down to the list of objects and double-click Display Shutdown Event Tracker
• Click Enabled
• Verify that in Options, Shutdown Event Tracker should be displayed: is set to Always
• Click OK

You will have to select a reason for the shutdown, like so: