I know how to enter fullscreen once it's already loaded in a window. This causes an ugly effect where, when I click its icon, briefly flashes a windowed window which immediately goes fullscreen. I hate that effect.
How do I make it actually start, right away, in fullscreen, without ever being in windowed mode even for a split second?
You just need to put fullscreen: true in your manifest: https://docs.nwjs.io/en/latest/References/Manifest%20Format/#fullscreen.