summary element has an arrow to display to the user whether the contents are being displayed or not. This is good for a quick mock of an idea, however a lot of projects may wish to modify the styling of the arrow to fit their design. As things are now, only Chrome (possibly Safari) via
summary::-webkit-details-marker exposes a way to touch the styling.
We should have a specification for how to target the details marker. This way developers can use standard CSS to change its color, or hide it in order to do their own styling. Could we possibly use
::details-marker as a new pseudo element for this?