This is how folded headings are supposed to work. I’m sorry that they don’t work in the way you expected. You can write between folded headers, but in a slightly different way than you are expecting. This is because everything that is “smaller” than an element is supposed to be encapsulated in it. If something is of equal importance, it will not be folded under the other element that it is equal to. Here’s an example:
Big idea
Everything here will get folded into unless it is of equal “importance” (another h1 element).
Smaller Idea
This is supposed to be a subtopic of Big Idea. If you fold this, everything under will fold until there is something of equal (h2) or bigger importance (h1).
Smaller Idea 2
This is another subtopic of Big Idea, but separate from Smaller Idea. It will get folded under the h1 element because it is a subtopic, but it will not get folder if you just fold Smaller Idea because it is of equal importance.
Even smaller idea
This is a subtopic of Smaller Idea 2. It will get folded under Big Idea and Smaller Idea 2 because it is a subtopic of those elements. Since it’s not a subtopic of Smaller Idea, it will not get folded under it. Things that are under this and are bigger (h1, h2) or equal (h3) will not be folded if you just fold this element. Smaller elements (h4, h5, h6) will be folded.
I hope this helps! If you’re not familiar with HTML, headings can be confusing. The “Nesting” example on this page might be helpful if you are still confused:
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/Heading_Elements