Currently the folding/unfolding feature applies in the current edit window only. If one leaves the edit mode - either by switching to the view-mode or by re-opening the current editor - all folded states get discarded. There is a feature request on this - Remembering heading and indent collapse in notes - #4 by PhDResearch
Yet, even if that one is implemented, we won’t get the power of folding in the view-mode. Why do we fold? To hide the details and to focus on the main structure. Then why losing this instrument right away after switching to the view mode?
I understand that folding and unfolding is not supported by markdown. Hence I propose this as a feature when preserved state is implemented. I believe it won’t be difficult to apply folding states to the same document but in the view mode.
But ideally I would engage meta-declaration somewhere inside the =document itself. IIRIC there’s such an initiative already as to use the document itself. Not a new thing at all if you -*- understand what I mean -*-