When an image has been opened in the Pix viewer, the user
has the option of enabling or disabling a thumbnail pane, which
shows the other images in the folder as thumbnails. This feature
can be toggled with the ViewThumbnail Pane
command, or by pressing F8.
The thumbnail pane may be positioned along the bottom of the
main image, or along the side. This is controlled by the settings
in EditPreferencesGeneralThumbnails in Viewer.