At the moment the Save Game Feature in TSW 3 has been disabled due to the fact that its bugged and screws up your save game. They are working at fixing it and re-enabling it at somepoint. Hentis
If you are on PS5 then you do have the option of quick resume which would serve as a workaround for save Edit: Have tried this but TSW has to load from scratch, so progress is lost on loading. Sub Edit: Maybe a possible solution for gen 9 consoles to implement quick resume?
Here’s the latest (I think) update. They are working on it and it’ll be soon from the looks of it. Thanks DTG JD for making this a priority. I for one am very very grateful this is getting taken care of. https://live.dovetailgames.com/live/train-sim-world/articles/article/player-update-tsw3-week-2