So you want to tag them some how so you can batch adjust each group in NX?? Since you have Lightroom, you might try doing a sort by ISO to start, then either assign a keyword, save to a Collection, color code or star rate if you want to be able to access again later, then do a batch rename of the images in Lightroom with an appropriate name to differentiate. Then when you open NX, you can pull them in by name.
If for some reason you are opposed to using Lightroom you should be able to do this with just about any database program.. PhotoMechanic or the like comes to mind.
Well...if they are going in LR anyway.. I'm assuming you use LR for cataloging etc..and NX for localized editing.
If you computer is halfway decent, the process I describe can be done in no time. In fact, you set up develop presets that will sort by ISO, tag or keyword and even get sorted to a Smart Collection all at import.