I originally installed this plugin to insert material for Google Analytics. Then I later added information for MailChimp and for Facebook Pixel. However, as an unexpected plus it has also been great for styling HTML elements that remains constant across themes. When I install a new theme, I don’t have to worry that I have lost custom CSS work, nor do I have to re-create it in a new child theme. As soon as the new theme is installed, I can see my CSS at work.