A traditional mod is usually a zip file which contains the following files (or some of them):
- def (folder)
- automat (folder)
- vehicle (folder)
- material (folder)
- manifest.sii
- description.txt
- mod_icon.jpg
These folders or zip files within the Workshop mod should have their contents similar to a traditional mod which means you should pack those as a ZIP and place that in your mod folder for it to work.
Here is an example of my Real Eaton Fuller Transmissions mod's file structure from Steam Workshop:
- legacy (zip file)
- def (folder)
- material (folder)
- manifest.sii
- mod_description.txt
- mod_icon.jpg
- universal (zip file)
- def (folder)
- material (folder)
- manifest.sii
- mod_description.txt
- mod_icon.jpg
- versions.sii