mx.controls.Slider/HSlider/VSlider

How to add and removes thumbs:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical">
   <mx:Script>
         <![CDATA[

         public function add(event:MouseEvent):void {
            slider.thumbCount++; // add new thumb

            //! if you don't set the value of the new thumb all thumbs will reset
            // thumbCount-1 is the last one added
            // 5 is a number i randomly picked
            slider.setThumbValueAt(slider.thumbCount-1,5); 
         }
         public function remove(event:MouseEvent):void {
            var index:int = 0; // the index of the thumb to be removed, indices are constant even with allowThumbOverlap="true"
            slider.thumbCount--; // remove thumb
            var values1:Array = slider.values; // get values of slider
            values1.splice(index,1); // splice value at index out or the last one will be choped of by default
            slider.values = values1; // set updated values
         }
      ]]>
   </mx:Script>
   <mx:HSlider id="slider" thumbCount="2" allowThumbOverlap="true"/>
   <mx:Button click="add(event)" label="add"/>
   <mx:Button click="remove(event)" label="remove"/>
</mx:Application>