thank you all for the hints
I succeeded in doeing what i wanted by creating a new handle in an empty sweethome 3d file, selecting it all and exporting it as an new .obj file
and than importing it as furniture and than combining it with an existing cabinet

is it possible to change existing furniture? I do not mean visible or color or structure but let say on an existing kitchen cabinet change the
cabinet handle by an other model?http://www.sweethome3d.com/support/mvnp ... on/sad.gif