Awesome, thanks for your feedback!
Glad the .obj file works in all of them, that's very good to know!
Sorry about the misunderstanding with the import function (I really have to start writing a manual), you cannot re-import the .obj file (I know that's confusing). You can only import two3D objects (*.23d file) that you have previously created, because they have a special format and are different in how they handle materials etc. (An .obj file does not hold that information anymore).
Clicking "add object" should give you a dialog that lists all the other objects you previously created and saved with two3D. Currently it just lists everything from your main data folder (to find out where that is click "about" in the main menu) as I have no "select folder/file" dialog yet - will add that in the future.
Saving a new file overwrites the old one? You mean in the editor itself or with the export function? Because the editor itself should not overwrite a *.23d file. But the export function currently does, that is correct. As that can create multiple files I found it easier to just overwrite as I thought the main reason is to modify the object and export again to update the exported files. Hm. What behaviour would you expect? Could detect first (before starting to write all export files) if there is at least one file that would be overwritten and in that case pop up a dialog to ask if overwrite or abort? Or select folder for export (once I have a folder select dialog).