I needed to use JsObj:
def render =
"#jsonScript *" #> js.jquery.JqJsCmds.JqOnLoad(
js.jquery.JqJE.Jq("#mylist") ~> js.JE.JsFunc("sortable", js.JE.JsObj(
("placeholder", "ui-state-highlight"),
("stop", js.JE.AnonFunc(SHtml.jsonCall( JE.Call("jsFunction"), liftFunction _)))
))
).cmd