In EndNote 20 and 21, the Summary panel is located at the right of the EndNote library window. It shows reference details and a preview of the generated citation. This panel is where you can edit a citation's details when clicking on the Edit tab, and preview and annotate the article in the PDF tab (if it has been imported).
If you close the Summary panel, you can open it again by double clicking on a reference in the centre Reference List pane.
