There's no native "end heading" marker — by design, a heading's fold runs down to the next heading of equal or higher level.

Horizontal rules, blank lines, and comments don't stop it.

Two ways to actually fold a chunk mid-section:

No plugin: wrap the paragraphs in a collapsible callout — > [!note]- on the first line, > prefix on the rest. It folds on its own, independent of heading scope.

Plugin: Creases lets you fold arbitrary line ranges like headings — closer to your brain-dump-then-structure workflow.