There is menu item "Invert Sorting Order", you can apply it each time after sorting by needed criteria.

What about sorting in reverse order?

When you sort by Name, it treats numbers by their numerical value (not by their ascii code), therefore it should work exactly the way you need.

Could there be an option for "Sort Folder Content by..." number?

I have notes with dates and I would like to call them up by earliest or latest, so maybe even a low to high sort and a high to low.