Hi Alex,

re:
> Here is a more clear example I have opened a DXF in MOI ( My default DXF Viewer)
> but when opened no reference to actual file is kept.

Yes, that's how it is intended to work. The reason why is because MoI will write to the current active file name when you use the Save command or when you exit MoI and choose "Save changes". But MoI is only able to save a subset of its possible information to a .dxf file so if you were to make something that MoI does not write to .dxf files you could end up thinking you had saved your complete work while actually only a subset was saved to the .dxf file.

To avoid that data loss scenario, MoI will only set the current file name when you open a .3dm file since that's the file format that MoI can store all of its information into.

- Michael