does someone know how to specify the height of the each line in a list widget using html?
You can set height “auto” for list items (type property) and define the height via template:
{
view: "list",
template: function(obj){
return "<div style='height:"+(obj.id%2?50:20)+"px'>"+obj.title+"</div>"
},
type:{
height: "auto"
},
...
}