Watermarks should be a viewing option in library view and not just on export.
Exporting watermarks is not very useful because in most cases you don't want the watermark on 1 location on the image.
Position, Scale , Opacity are all parameters that change with every image to get the perfect spot for your watermark.
If watermarks would be a viewing option in library view the user can easily position, scale etc. the watermark.
On final export you can turn it on or off.
I think this would be a very welcome feature.
This a user to user forum.
Feature requests should be made here: http://feedback.photoshop.com/photoshop_family/products/photoshop_family_photoshop_lightro om either by adding your vote to an existing feature request or, if none exists, creating one.