Sorry for an answer in English.
Maybe there is some misunderstanding. I am able to 'Save a shape' which is the English equivalent of 'Form speichern' when I have changed the form of the shape. Mostly that happens after converting the shape to a freeform shape and editing the points. You'll see such a custom shape in the movie in this blog post, second slide: Custom Short Answer Question - Captivate blog
'Save a shape' is not meant to save changes to fill or stroke for the shape, in that case you should save a shape style. Use the Object Style Manager, and save the shape style. Each shape style can even have the three states (including rollover and down) that are needed if the shape is used as a button.