None, at least not directly. It's an allotrope which can only exist under extreme physical conditions.

There are many such allotropes of well-known substances. For instance, solid water has over a dozen allotropes (including ice-IX, or "ice-nine", which will not turn you into a human popsicle). Most of the interesting allotropes of ice only form under pressures of >100 MPa, so they are never seen under terrestrial conditions. The same applies to most other allotropes, with a few notable exceptions in metals and metalloids (like tin and sulphur).

It's unclear to me what the author of the article had in mind when they suggested the "potential" that "black nitrogen might have for electronics". Unless the author is imagining electronics which must be placed under immense pressure and heated to thousands of degrees to remain stable?

I was told, that at nanoscale high pressures in the gigapascal range are attainable somewhat easily by a friend of mine working here: https://tu-dresden.de/ing/elektrotechnik/ihm/NEM/die-profess... so maybe this form of nitrogen could be in special nano-islands or something like that. I guess, it is important to understand the physics of the materials to a certain degree and then think about engineering. This research is clearly at the beginning of the first phase, so they maybe found some interesting properties that could be useful in electronics but that's about it.

If it has good conductivity, they probably just write in "potential for electronics" out of habit or reflex. It's probably good for science fiction writers to be able to find this stuff.

There's always the possibility that a method will be found that will allow the material to maintain at least some of these properties after "returning" to normal temp/pressures conditions.

That seems unlikely for a compound which is stable as a gas at STP. You can sometimes stabilize an allotrope of a compound which would otherwise be stable as another allotrope, but there's no real way (that I'm aware of) to stave off a phase transition, especially one as energetic as solid/gas.

My ignorant guess: During a manufacturing process?

This actually bugs me about articles on new discoveries: they almost always try to talk about potential applications, no matter how far-fetched they are. Sometimes the most honest answer is that we currently don't know any potential applications.

In this case, we have something that may be similar to graphene, but can only exist at 4000°C and 1.4 million atmospheres. Graphene is interesting for electronics, so they suggest black nitrogen might be useful for electronics too. But of course graphene has the slight advantage that it's relatively easy to produce and doesn't dissolve at temperatures lower than the surface of a star.