Hello,
I would like to remove the shadows of my side panels. So after search I found only this:
http://askubuntu.com/questions/194001/r ... in-kde-4-8
and this empty wiki entry:
http://community.kde.org/Plasma/TakingA ... w_from_Svg

So I'm wondering: Is editing the svg from hand still the way to go or is there an option now?

TIA

No, there's no option. One possible workaround would be to copy panel-background from theme's opaque/widgets/ dir to widgets/ and/or translucent/widgets/. But there's no guarantee that the themer didn't draw shadow in the opaque svg also.
That is, if you do not want disable compositing.