Ability to set the transparency on the dots/circles of a scatter plot. If you have many dots on top of each other, then setting the transparency to a low value like 10% allows you to see the density ...
More specifically, when clicking legend items, the transparency of the unselected items is insufficient - it's very hard to tell what was selected in a large set. This should be configurable (seems to default to around 40% transparent, I would want closer to 80 or 90).
