Hi Marcel, I think I see what you mean now.

It was a problem in MoI v1 where if you did a File/Export to a mesh file format, that once your export was finished those objects would be deselected. This was a side effect from the main objects being hidden temporarily so that you could see the generated meshes.

This has been solved in MoI v2 (including in the current beta release), so that the original selection is now preserved when you complete the Export.

So if you are using v1 you will need to reselect your objects in order to delete them, but in v2 you can just hit delete.

- Michael