Hello!
The nestedList requires a tree store as it has multiple level. If you need a single-level list, use the plain List component, as the example above.
As for customizing the display of the NestedList, something like that should get you started:
<%@ Page Language="C#" %>
<!DOCTYPE html>
<html>
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<ext:ResourceManager runat="server" />
<ext:NestedList runat="server" ID="nl1" Title="Restaurant Menu" FullScreen="true">
<ListConfig>
<ext:List runat="server">
<ItemTpl runat="server">
<Html>
<div style="display:inline-block; width: 10%;">
[{checked}]
</div>
{text}
</Html>
</ItemTpl>
</ext:List>
</ListConfig>
<Store>
<ext:TreeStore runat="server">
<Model>
<ext:Model runat="server">
<Fields>
<ext:ModelField Name="text" />
</Fields>
</ext:Model>
</Model>
<Root>
<ext:Node Text="Menu">
<Children>
<ext:Node Text="Drinks" Icon="Anchor" Checked="true">
<Children>
<ext:Node Text="Water" />
<ext:Node Text="Beer" />
<ext:Node Text="Whiskey" />
<ext:Node Text="Wine" />
</Children>
</ext:Node>
<ext:Node Text="Dishes" Icon="Application" Checked="false">
<Children>
<ext:Node Text="Rice" />
<ext:Node Text="Beans" />
<ext:Node Text="Meat" />
<ext:Node Text="Salad" />
</Children>
</ext:Node>
</Children>
</ext:Node>
</Root>
</ext:TreeStore>
</Store>
</ext:NestedList>
</div>
</form>
</body>
</html>
Hope this helps!