In this post, Vadim Tabakman suggested going to Site Settings > Message Templates or Central Admin > Nintex Workflow Management > Message Templates to edit the notification headers, templates, and footers. I've been to the former and it only shows the Approval notification. I am not the Sharepoint admin and am not sure I can get to the latter--which templates are located there? Flexi task notifications? To-do task notifications? Plain-old "send notification" notifications?
Thanks in advance!