Inspired by the way the Expand/Collapse feature works in search results (you can Expand All), I would like to see that option available also in the Library (and the Collections result pane) when the view is grouped by one field. For example, if I sort by Author, it groups them with each author's books collapsed under the person's name, so I can't actually see my whole list of books unless I expand each author's name. I'd love to be able to do that all at one click.
The Cited By tool is another example of how I'd like to see the Library and Collections result pane work:
