[folding] Show tooltip on hovering collapse markers

[waldyrious]

It would be nice to be able to hover the ⊞ and ⊟ symbols in the left gutter of the editor and see a tooltip saying what will happen if they're clicked*, and showing which keyboard shortcut (if any) is assigned to the action, thus making the UI behavior more discoverable.

_{* This may sound superfluous, but IMO it would help with promoting consistent nomenclature throughout the interface, e.g. "collapse"/"expand" vs. "fold"/"unfold" vs. "hide"/"show", etc.}

[dbeigi]

Hi @waldyrious, can you provide a screenshot of where these are?

[waldyrious]

@dbeigi actually the icons have been changed in 1.37: instead of ⊟ and ⊞, they are now arrowheads, looking like v and >, respectively. Here's a screenshot showing the new icons, taken using the latest release, 1.40: