Outlines in OneNote vs outlines in Scrivener

I’m testing Scrivener to see if it will help me better manage all the chores involved in writing a novel. I’ve been using OneNote. But I think I’m running into a semantics issue with exploring Scrivener.
As I understand it, outlining in Scrivener means creating a hierarchical structure of where certain documents should appear (inside chapters, chapters inside parts, etc.). But in OneNote, outlining can mean how the manuscript is organized but (!) outlining can also mean (as I use it) organizing my thoughts on a particular chapter (for example). (Like when you had to organize an English paper in high school.) Remember this, better check on that, is there a better way to say this, here is the backstory. And with OneNote I can collapse the outline of these thoughts in various ways to focus on what I’m concerned about at the moment. Can I do that in Scrivener? If not, then I’ll have to create some good-size non-outline versions of my notes, which I am loath to do.

Based on what I understand from your post, I’d say either host these collapsible inside the concerned chapter like this:
Draft folder
. Chapter
. . . Related notes
. . . . .note 1
. . . . .note 2

So this way you can collapse “Related notes” (of course name it what you want), thus hiding the notes that are inside, while still having access to the chapter itself.

Or, another way would be to host “Related notes” elsewhere in the project (research folder, for e.g.) and use document’s bookmarks.

Perhaps even using comments so that you have notes somewhere precise within the body text could suit your needs better.
Same goes for document links.

Lots of different ways to accommodate one’s process, actually.
I only here mentioned a few.

Outlining in Scrivener creates a hierarchical structure for documents in the Binder. The relationship between that structure and your manuscript is up to you.

If you haven’t already, I’d recommend taking a look at our Interactive Tutorial, available from the Help menu. It’s a good overview of fundamental operations like this.