Permanently change Safari Custom User Agent editing the plist file

Hey everyone. I need help with changing Safari's user agent permanently by editing the plist file

Usually one would go to "Preferences > Advanced > Show Developer mode in menu bar." Then "Develop > User Agent > Chrome - windows" for example. However, when you open a new tab or window, this goes back to Default (Safari). This is expected behaviour.

In the past, it was possible to edit a line that determined the user agent in "/Users/(user)/Library/Preferences/com.apple.Safari.plist"

There was a line called: 'CustomUserAgent'. It's not there anymore. How can I create it (with defaults probably) with the user agent of Chrome (Mac)? Alternatively, is there another way to change it, or has the procedure changed? I called Apple Support to no avail.

Thank you.

Edit: Forum article for reference. This is an old trick as the CustomUserAgent string is not there anymore

http://hints.macworld.com/article.php?story=20090630112653430

This would be helpful as a way to stop Gmail from nagging users to switch from Safari to Chrome.

Permanently change Safari Custom User Agent editing the plist file
 
 
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