+1 for this feature from me as well.
I created a workaround which seems to work pretty well. In my case I only need to display multiple ranges (read-only), but I'm sure with a bit of javascript work it could be made to be editable.
First add a slider to the page. This will cause the web resources for it to be loaded. If you don't use RadSkinManager you might have to set the skin here as well.
<telerik:RadSlider runat="server" ID="rslSlider" style="visibility:hidden"></telerik:RadSlider>
The multi-range slider is then just a few nested divs (elsewhere on the page):
<div id="divTrackBar" class="RadSlider RadSlider_Forest" runat="server">
<div class="RadSlider rslHorizontal">
<div id="divTrackInner" runat="server" class="RadSlider rslTrack" style="width:200px;">
<div class="RadSlider rslSelectedregion" style="width:50px; left:20px;"></div>
<div class="RadSlider rslSelectedregion" style="width:50px; left:120px;"></div>
<a class="RadSlider rslDraghandle" style="left:20px;" title="tooltip text"></a>
</div>
</div>
</div>
If you use dynamic skinning you can set the skin on Page_Load:
protected void Page_Load(object sender, EventArgs e)
{
divTrackBar.Attributes["class"] = String.Format("RadSlider RadSlider_{0}", skin);
}
The ranges & handles can also be added in code behind:
divTrackInner.Controls.Clear();
//Add a selected range
HtmlGenericControl item = new HtmlGenericControl("div");
item.Attributes["class"] = "RadSlider rslSelectedregion";
item.Attributes["style"] = "width:80px; left:120px;";
divTrackInner.Controls.Add(item);
//Add a handle
item = new HtmlGenericControl("a");
item.Attributes["class"] = "RadSlider rslDraghandle";
item.Attributes["style"] = "left:120px;";
item.Attributes["title"] = "tooltip text";
divTrackInner.Controls.Add(item);