Due to the lack of international forums I make this here bi-lingual, even if modern translation sites don't make it really necessary but maybe some search engines will have easier times finding this.
So "V5.0 Final Edition" is out in Japan for quite some time and - who was able to import, probably did. And applied unofficial English or German language patches. Who not, here is a quick summary:
After the game came out, some add on packs were released. At the end it contained 325 trains. If I remember correctly, V4 Masters Edition in Steam had 100 trains, most likely due to licensing.
However, There is a nice box sold as "V 5.0 DX" containing a thick book and all but one Add on (Train Kit 2).
in November 2024 V5 was released to Steam to Japan region plus the A-Train 9 Train Construction ("A9TC" for short) program, which is globally available. This game is advertised as "V5.0 DX+", most likely containing the Train Kit 2 which brings additional 25 trains to the game. Whats special with this release - you now can make your own trains and import them to the game. It also works with the boxed edition, provided the game is patched to build 5205.
Also end November 2024 ArtDink announced the international release of V5 to steam. But currently it is unclear to what extend the included trains will be.