You can not load planets, if you try to you will simply see the ship you were editing before or a blank screen (if you just started the program up). I have no idea what happens if you start editing at that point, is it saving changes to the planet or the ship you loaded before? Including the model name in the title bar would be helpful in that regard and for those of us who want to make a lot of variants. Also, loading a planet seems to prevent the path from saving.