There are two different things: UV can display a file alone, but a manifest is needed, and the plugin creates the manifest only for the item level (and for the collection level too), so currently, it’s not possible directly to display one file only: no $this->universalViewer($file).
Nevertheless, there are three solutions that can help currently:
- use the filter
uv_manifest, for example to remove all images except the one you want;
- use an alternative manifest, that you can built it somewhere, and set the url in a field of the item;
- try to modify something somewhere in uv to display the file only (the discussion).
The first solution is the easiest.