How to enable new Firefox Preferences page now

In currently Firefox Stable, Beta or Aurora when you enable Firefox Preferences page you will see this popup window (CMD+,) or Firefox Menu and choose Preferences

In Firefox Nightly by default if you access your Preferences page you will see this new dedicated page (Preferences in content)

If you want to get this new page on any other version of Firefox now you can easily enable this in your about:config and search for browser.preferences.inContent and change the value from false to true.

You will now have new Firefox Preferences page :)