Click the expand/collapse button, 
, on the top left corner of the key image panel.
Position the cursor over the separator and when the cursor changes to a bi-directional arrow, drag the separator.
Key images selected for a particular study, and usually referenced and/or attached to a report, are displayed in key image panel at the bottom of the report panel.
To resize the key image panel, do one of the following:
Click the expand/collapse button, , on the top left corner of the key image panel.
Position the cursor over the separator and when the cursor changes to a bi-directional arrow, drag the separator.
Key images can be displayed as a single series in the Presentation Group section of the thumbnail panel. To show or hide the key image series in the thumbnail panel, check or clear the Show Key Image Thumbnails checkbox under the Settings tab in the Customize Settings panel.
Key images can be manipulated from the key image panel. Changes are saved if the report component is not Final. You can also drag the key image from the report panel back to an image frame for editing. However, changes made to the image in the image frame are not applied to the image in the report panel. To save the changes, attach the updated image to the report panel as a new key image. Remove the old one, if necessary, by right-clicking the image in the report panel and selecting Delete.