thanks a lot Martin !
he could add a default setup javascrpit file in the look and feelpackage he's using. a proper named javascript file is executed every time a plasmoid is added, this is designed for distributions that want to have a different default or the plasmoid.(in look and feel package, plasmoidsetupscripts/plasmoidpluginname.js) for instance ~/.local/share/plasma/look-and-feel/org.kde.test/contents/plasmoidsetupscripts/org.kde.plasma.analogclock.js -- Marco Martin