I played TSW and all my dlc tracks and trains were gone, I can only play CSX heavy haul. I can manage my DLCs in steam and they are all installed, but I cannot see them in my game. Even in game dovetail games store there are all DLCs with prices inder the pictures, that means I can buy them and I do not own them, which is weird cuz I own them even steam says that but game not
I am not sure how the dovetail games store knows what you have, so I would not worry about that. While I have not experienced your own problem, I have had to do a number of unistalls and reinstalls on my laptop to get the DLCs I want without running out of disc space, and I suggest you simply do this. Just make sure that all the DLCs are checked in Steam before you reinstall. It might take some time, but it is probably the only way to get them back. It might be worth copying your My Games\TS2Prototype\Saved folder in My Documents first, as some people appear to get their character information and acheivements wiped when they do a reinstall.
Have you tried opening Steam, going to Library, finding "Train Sim World 2020" in the lefthand pane, right clicking it, selecting Properties, choosing the Local Files tab, and clicking "Verify Integrity of Game Files"?