Thanks for your speedy reply! We thoroughly reviewed the ‘edit code’ section of the Newsletter plugin, but could not find a “custom CSS” section/heading as you instructed. Is the window shown under Plugins˃ Edit Plugins˃ Newsletter˃ newsletter/admin.css the correct area to add this code? There are many sub-sections listed on the right-hand side, but there isn’t one called “custom css.”
Or is it necessary that we install this plugin to add the custom CSS?
Sorry for any complications and thanks in advance for your help! 🙂