It’s technically possible, but not within this add-on.
Exporting a DNG is essentially just applying a mask to the rendered image to simulate a Bayer pattern. When you do this, you intentionally “lose” color information that your demosaicing software (RawTherapee, Lightroom, etc.) later reconstructs using its own algorithms.
Importing DNG files, however, is a completely different task. You would need to implement the full DNG processing pipeline, including demosaicing and other raw-data handling steps. I’m sure Python libraries exist to help with this, but integrating them into a Blender add-on is not that simple.
At the moment, I only have enough time to maintain this add-on, so developing another one with full DNG import support would be difficult for me.
So is it possible to add the feature to import DNG files?