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"Thumbnail" display application for preview images.
The "Viewer" display application to display an original (file) via the corresponding icon.
the "Viewer" display application to display a "standard" original for the object (file displayed by default for the object - e.g. document or material).
Goto SAP Customizing Implementation Guide → Cross-Application Components → Document Management → Visual Enterprise Generator → Define Search Sequence for Viewable File to edit these settings.
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