NSExtensionServiceFinderPreviewIconName
The name of an icon for display when the extension appears in the Finder Preview pane and Quick Actions menu.
Discussion
This key is used in conjunction with the NSExtensionServiceAllowsFinderPreviewItem key.
Set the NSExtensionServiceFinderPreviewIconName key’s value to a system icon name or the name of an icon in the extension bundle. This icon should be a template image: a monochromatic image with transparency, anti-aliasing, and no drop shadow that uses a mask to define its shape. For design guidance, see Human Interface Guidelines > macOS > Custom Icons. If no icon is specified, a default icon is used.