A Button (or even a command) to Fold/Collapse All Markdown Headings within the Notebook Itself.

[AaronPedersen-QUT]

I mean, I think the title kind of says it all really, there's not really much to this request; but as small as this feature is, its absence is massively felt.
And by "Markdown Headings" I am of course referring to the Markdown cells with a # Title or ## Heading formatted line within.

I have noticed that there is this exact feature for the "OUTLINE" navigation menu,
the menu under the "OUTLINE" tab at the bottom of the "Explorer" margin, that comes up when you press ( ctrl + b ):

But as far as I have seen (and read about), there is no such feature for the Notebook itself.

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Just something like this for the Notebook itself would be a godsend, because it is honestly a slight pain in the rear to have to collapse every single heading, sub-heading, and sub-sub-heading individually, every time I close and re-open the VS-Code application and SSH back into my LINUX laptop.

[DonJayamanne]

@amunger @Yoyokrazy /cc