Not sure how feasible this is, but there have been many times and places where I would have loved to explicitly
- Require a scroll bar in a panel, e.g., so that you didn’t have to scroll the entire page to see or reach something you needed. (When you scroll the entire page, a lot of context scrolls away, too.)
- Prohibit the appearance of a scroll bar, so that it doesn’t obscure something else of importance.
- Allow a scroll bar (the “I don’t care – so far” scenario).
I’m not sure how best to implement such a thing. Would it be a new kind of container? Or a property added to existing containers?