Try to save them as absolute file or as user objects.
When you save them as user objects, the will be added into the objects.txt
If you save them as absolute file they will be added into a abs_yourname.txt
where "yourname" is a name you choose.
When working with scenery objects, its important to set the object visibility
in VSF to 100% or objects out of visibility range will be hidden and not saved. The same goes for object complexity.
Once you've saved a absolute file you may then add it into the objects.txt by clicking the button "add absolute file".
Try it and let us know