Is there any software that allows designing the icon of a Modelica component, and then copy into Dymola? It is hard to draw the picture in Dymola.
A short summary of the answers, there is 4 software support this task:
For some tasks OMEdit is better. Properties of graphical elements are nicely presented in a single dialog and you can easily edit the points of lines and polygons.
As an alternative you can use svg and png files, which can be nicely drawn with Inkscape.