A disadvantage of using the free edition of DesignSpark is the inability to mirror any solid object. For a printer, which needs most parts on both sides, this is inconvenient. So I created all parts on one side, exported them as .STL, and used Cura to mirror them. Afterwards it is also possible to import the mirrored parts into DesignSpark. But the imported parts are less easy to edit than the originals since they now now longer consist of basic shapes. So all rounded corners and holes are now multi-facet surfaces, which makes them cumbersome to handle.