Hi, I am new to NLP but not to inverting negatives. 
I found that NLP does an incredible job getting usable images in no time. However I do miss a function to set and lock the white balance across a whole film roll.
In my case I love to shoot with a fixed WB (daylight) when I shoot digital, and so do I with film. It’s a matter of taste but I prefer to keep the ambiance of a lighting and then choose to edit if an unpleasant color cast is present. To be honest I do not edit much the WB (except for indoor lighting, and then I balance for tungsten or fluorescent).
Although it’s possible to adjust the WB in NLP with the mid tones sliders, it can be very hard with mixed lighting or complexe color scene. I do found that using a neutral target to be very helping. To do so, I shot a neutral frame (Nikon F5 + Nikon ES-2 + flash).
Then here is my process with NLP for an image:
- White balance set to film border for image
- White balance set to film border for neutral frame (same as image)
- Convert image with NLP
image is cooler than expected - Sync scene of the previously converted image with the neutral frame (the neutral frame often turn blue)
- On the neutral frame I manually adjust WB in Lightroom (matching RGB channels on the histogram) to obtain a grey
- Copy the new white balance to the original image image is now well balanced
My request would be to be able to do so directly in NLP (maybe selecting a neutral frame in the convert dialog box).
Hope it helps improving the already great NLP
Edouard