I don't think your operating system has a built in way to show previews of a DNG file. There are probably plug-ins/add-ons that can allow your operating system to show thumbnails of DNGs. Since I'm not a Mac person, someone else will have to provide details (or you can use a search engine to find such a thing)
Why are you exporting DNGs anyway? Exproting as DNG is only useful if you want to transfer the file to certain other Adobe software.
Thanks for your reply.
Mac does support previewing dngs in finder and preview. This has not been a problem before (besides when using my fujufilm compact camera, which mac now has updated the Apple camera for).
To answer your Q about dng files. Thats exactly what i do. I have work which involves communicating/transfering multiple lr -edited files to someone else whom further edits in ps. Not only that, I personally use dng as a way of storing my files. I suppose like to keep my files tidy and uniform.
Any mac users out there who has a a solution to my issue with previewing dngs?