This series doesn't have special episodes.

I suppose that you are talking about the 3 theatrical movies that were released after the end of the series. They are listed in the movie part of our database:

• Kabaneri of the Iron Fortress Recap 1: Gathering Light (2016)
• Kabaneri of the Iron Fortress Recap 2: Burning Life (2017)
• Kabaneri of the Iron Fortress: The Battle of Unato (2019)

and should not be duplicate as special episode.

Another possibility is that you refer to the 3 parts series released by Netflix in 2019. This series is just a recut version of the 3rd movie listed above and,as such, is considered as a duplicate and shouldn't be listed here.

I am referring to the 3 part series released by Netflix. I am aware that it is a recut, however anime recuts have a long history of being considered specials. Take the infamous *.5 episodes, which while sometimes creatively done are fundamentally just recuts of the existing season. Or recap movies, which essentially take a handful of episodes and recuts them into a movie. What Netflix did was the reverse; they took a feature length movie and cut it in such a way that it could be considered 3 moderate length specials, not unlike Demon Slayer Mugen Train which exists in TMDB as both a Movie and Demon Slayer Season 02.

Just my opinion, but I believe the Netflix cut absolutely qualifies as a Special.

As indicated, the Netflix series is a simple recut of the movie without additional scenes. As such, it can't be listed here.