You might already know that steam can simply delete Workshop-Mods from your hard drive.
What could wreck your whole savegame in Transport Fever (1) can still have unfortunate effects in TpF2.
To avoid this issue you can invest some time, but therefore save your savegames.
2 save Steam-Mods
2.1 Download Mods
Downloading works as usual - just click Subscribe and wait until the download is ready.
2.2 Find Mods
The downloaded Mods are saved unencrypted on your hard drive.
The directory can be found here:
Win c:\Programme (x86)\Steam\steamapps\workshop\content\1066780\
Mac /Users/<username>/Library/Application Support/Steam/steamapps/workshop/content/1066780/
1066780 hereby is the number assigned to TpF2 by Steam.
In this directory you'll find some more folders, which all have a multi-digit number as a name.
Every one of this folders is one Mod.
2.3 Copy Mods
The Mods from this folder have to be copied into the User-Mod-folder:
Win c:\Programme (x86)\Steam\userdata\<steam userid>\1066780\local\mods\
Linux ~/.steam/steam/userdata/<steam userid>/1066780/local/mods/
Mac /Users/<username>/Library/Application Support/Steam/userdata/<user-number>/1066780/local/mods/
Afterwards, a _1 has to be added to the folder name. This is to valiate the mods for Transport Fever 2 (otherwise it will be displayed as ***<foldername>).
I personally would also add author and name in the middle (this can be looked up inside the folder in the mod.lua)
At the End the Mod should be named 0000000000_1 or 0000000000_author_modname_1 (while the zeroes stand for the individual Mod number).
2.4 Unsubscribe Mods
To avoid doubling, unsubscribe when done.
The mods will disappear from the Workshop-folder, but stay in the User-Mod-folder.
3 Update saved Mods
The saved Mods will not receive Updates by Steam anymore.
To update the Mods, you have to resubscribe to the Mod on Steam.
Afterwards you'll have to find the folder of the just downloaded Mod (compare: Find Mods)
and the folder of the saved Mod (compare: Copy Mod).
You can do that by using the multi-digit number that makes the individual Mods identifyable.
I recommend to save the saved Mod in another folder.
Firstly, delete the content of the saved Mod.
Afterwards, copy the content of the workshop mod into the now clean folder of the saved Mod.
Lastly, unsubscribe from the mod on Steam Workshop again.
The updated Mod should now be stored securely in your User-Mod-folder.