For me the concept of outlining is a really important for a basic text editor. I store written concept ideas and code snippets. So mainly pure text. But this can become a big amount of lines. So an overview like a table of content or toggle lists would help me a lot. I don´t want to use a 'middle man' like a word processor because i constantly switch between MacOS,Windows and iOS.
Another great way to use this concept is by reflection study stuff or preparing a meeting. Just write the topic or the question down and hide the answer. This is such an easy and useful method to remember stuff.
There are many more examples, but I just want to point out, that this not a basic feature, it's concept of organizing information and I hope that Evernote will implement this possibility.
Just my 2 cents.
Stay healthy!