As I understand (and use) it, an outline consists of one to many cells, arranged in the familiar ‘one parent / one or many children’ format.

In electronic outlines, you can collapse children and all descendants into the parent cell.

In your example, the parent cell consists of eight lines of text. There is no outline, and therefore nothing to collapse.

In practice, you can do one of at least two things.
1. Put the title of the article in the parent cell, and put the article in a child cell (or child cells). Then it’s simple to collapse the children into the parent.
2. NoteBook also allows one to reduce the entire contents of a single cell to just the beginning of the first line. This is called “Folded Text”. It is covered in the Help file, where it says “To hide all but the first line of text in a cell, select the cell and choose Outline → Show Full Cell Text.”

I use method #1 all the time. It works well for attachments (and images) too—I can reveal them whenever I want, but I like to mostly keep them collapsed into a “title” cell so that I am able to navigate the outline more readily.

Oops, I neglected to say I was talking about what happens when you put the outline up as a webpage. Then the children will not collapse with the “escape” key. So if you have 5 children under a parent cell when you open the parent ALL the children are unfolded. I’m really trying to use Notebook as a better type of presenter, where the reader gets to open each level as they wish, like you can do on the ‘normal’ outline page of a notebook. Sorry about not mentioning the webpage.