It’s possible. You should notice, that those dotted arrows and lines in main menu are in fact images. So to have submenu indicator you should remove this image and insert sub-menu arrow definition. For css-menu you can do this by editing ja-sosdmenu.css in ja-cssmenu folder. Find #ja-cssmenu li a { definition and comment a line which starts with background: url, then add a line
background: url(img/arrow-child.gif) no-repeat center right;
to section which starts with #ja-cssmenu li.havechild {. The rest is up to You. Good luck ! 🙂
