This feature was introduced with the new Grid table, which allows directly editable fields to have two modes of navigation to the entity: expand in current panel or open in new panel at the right.
Similarly, we can implement the Expand button in the (not directly editable) direct link fields such as the inline entity reference, list items, board cards, etc. In this case the ‘Open in new panel on the right’ button does not have to be show, since the direct link already has that navigation function.