Keeping raw image quality in Lr>Ps>Lr workflow

What's at the bottom of all this is that a raw file and a rendered RGB file are two very different things.

They will not, and they are not supposed to, react the same way to a numerical slider adjustment in Lightroom. The adjustments are working on different types of data that will respond differently. This is normal and does not in itself indicate data loss.

The reason a raw file can contain "hidden" highlight detail is that it is dynamically compressed. If you could see a raw file directly, it would look like an extremely flat and dull (and dark) monochrome image. When encoded into an RGB color space for output, the data are mapped into a much steeper and gamma-corrected tone response curve. This is necessary to produce a realistic image, but this is also where you risk highlight clipping if you aren't careful.

Is there a way to edit a raw, in my case a .NEF file, first in Ps and then in Lr without losing what seems to be the raw characteristics of the image?

There is another approach to your question, with a different workflow-

Select your .NEF image in Lr (be it the original or a VC) and then {Edit In > Open as Smart Object in Photoshop.}

Now in Photoshop you can edit the background 'Smart Object' layer in ACR (double-click the layer image thumbnail) with the 'same' adjustments as in Lr.

Note: This does not alter any adjustments you have made to the image in Lightroom.

To expand on what Todd Shaner​ and JohanElzenga​ said, do all your Exposure, Highlight, Shadows, Whites, Blacks and Tone curve edits BEFORE you send the to Photoshop.  Then you can edit in Photoshop and save a a PSD or TIFF using 16 bits ProPhoto RGB.   Saving as 16 bit results is big files but you throw too much data away using 8 bit.

Just as a note: you can’t “edit a virtual copy in Photoshop”. A virtual copy is nothing more than an extra set of edit metadata, belonging to the same original raw file. When you send a raw file to Photoshop, either selecting the original or the virtual copy, you will create a derivative tiff or psd. When that tiff or psd is saved, it will automatically be imported (as a new image) in Lightroom. It does not ‘update’ the virtual copy, it is a new image.

labasaskarolis  wrote The only issue is, to test to see if working on a .psd (the virtual copy which I edited in Ps) had the same quality as the original raw image, I created the same decrease in exposure for both images, but they came out differently. The edited virtual copy had a characteristically .jpg lack of contrast and loss of detail in highlights, while the original image behaved like I expected, the decrease in exposure revealing more of the details in the highlights.

This is most likely due to highlight clipping, which can be recovered in the raw file. To prevent this from happening at a minimum you should adjust the raw file or virtual copy's Basic panel settings BEFORE creating and editing the Edit in PS copy. Remove any highlight and shadow clipping by holding down the ALT key when adjusting these controls, which allows seeing the areas that are clipped.