Choosing a row in any section replaces whatever the margin is showing, and the picture stays in view as you read down past the section headings instead of being handed over at each one. It settles near the top of the window and only lets go at the end of the list. Because the margin is one column for the whole table rather than one per section, short sections no longer have to be held open to make room for a picture beside them.
One picture in the front page margin for the whole list
The margin now holds a single picture that follows the page through every section, rather than one per section.