What do you mean it didn't exist? Goku displayed SSJ2 against Yakon some 4 months before the movie released.
Did you even read what I just posted to you? Goku displayed SSjin 2 vs Yakon exactly 3 months prior to the movie release. Movie villians are as strong as the strongest character shown in the manga 3 months prior to the movie release.
You can see it here
https://dbzeta.net/threads/how-the-movie-releate-to-the-manga-and-the-anime.20128/
Movie 10 Broli is as strong as SSjin 2 Goku. Also it doesn't matter if it's shown in the manga because the movies are based on the anime and they don't go ahead of the anime as stated by Koyama himself.
[Takao Koyama]: In Japan, these anime movies that are based on manga, or especially TV anime if theyare all done concurrent at the time, are released on a two-movie-a-year schedule. Generally, around March and then July. Of course, we have to start working on these much far ahead of time of where we might even know where the story has gotten. But we have to put on a magician’s hat and predict how far along the story [will be] because the TV series is really prioritized. We cannot get ahead of their storyline. We have to work within the framework that exists or the one we suspect will exist by that time.
That alone should tell you the movies can't get ahead of the anime
You can clearly see that all movies contain only what the anime showed at that time despite the manga being pretty far ahead. The production for the movies start 3 months prior to the movies's release. That's why the villian is comparable to the strongest character in who appears three months prior in the manga because what else can TOEI do? Have you ever noticed to my argument over the years?
Also, Goku's appearance was totally irrelevant in movie 10. Goku specifically tells Gohan and Goten that they have to use all the power they have and that there ain't anything else.
The main power that killed Broli was Gohan and Goten. Goku just gave them his supporting SSjin ki It's a similiar thing to Gohan's beam struggle vs Cell. Goku is a a SSjin supporting Gohan in the anime. In the manga he is in his base form. Gohan also says in the anime that he felt Goku giving him his ki.
However the main power that killed Cell was Gohan. Same thing.
If you want me to explain in the depth about how the movies connect to the anime and manga, I would gladly do it but I don't like that it's being ignored. I was actually studying the subject for years and I can answer all your questions but it has to be taken seriously. Your question of how SSjin 2 Goku did not exist if he was using it vs Yakon in the manga is a clear indication it's been ignored by you.