Blender-O3D-IO is a new plugin for Blender (versions 2.79 - 3.4) for importing and exporting Omsi models. It supports importing .o3d, .sco, and .cfg files with full support for materials. The plugin can also export .o3d files (with .cfg and .sco exporting coming soon).
Please read the full description on WebDisk: Blender-O3D-IO Plugin for instructions on how to install the plugin.
As it stands the plugin is still in development so there will still be some bugs, please report them either on GitHub (link) or in this thread. If you have any questions please feel free to ask them here.
If you want to keep up to date with the development then you can star my GitHub repository: https://github.com/space928/Blender-O3D-IO-Public
Happy modding!