While it isn’t why I do it usually, backup is one. Exporting the part saves a copy in a directory not controlled by Fritzing which means I can restore Fritzing from a clean install then import the new parts from my backup if I need to. Another reason would be too many parts cluttering up the bins, so export the ones you aren’t using right now. If export doesn’t have a use then it shouldn’t exist. Given that it exists it should not corrupt the Fritzing state in such a way that you can not do anything except manually clear files. As I said I have a fix that registers the part files with the file deletion mechanism which does cause the files to be deleted if you say yes delete the files and will then let you reload it as it should, so I think it really is a bug.
Nope. The sequence is edit the part, save as new part, export part, shutdown Fritzing. At this point the shutdown asks if you want to save the new mine parts. Answer no don’t save the parts and it will not in fact remove the files in the user directory for the new part, it will remove the part in the database I believe as it is not in the mine parts bin on reload. When you restart Fritzing and try and load the part you will get the “part already exists” message because the files exist in the My Documents directory, but since Fritzing doesn’t have the part in the database you can’t delete it (because Fritzing doesn’t know it exists to delete I think because some of the references, just not all of them have been deleted). As I said this isn’t to do with editing the files outside only exporting a part and not saving the mine parts bin copy. I suspect if you say yes save the part, on reload you will be able to delete it successfully because the reload will populate the database correctly (but I can’t say that I’ve tried this either).
Peter