Flex Two Way Drag and Drop :-

In this tutorial you can see two way drag and drop for list based controls. In this example we can set dragEnabled="true" dragMoveEnabled="true" dropEnabled="true"  for both lists as you can see in this example.

Two-way Drag and Drop in Flex Example :-

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" creationComplete="initApp();">

<mx:Script>

import mx.collections.ArrayCollection;

private function initApp():void {

nameList.dataProvider = new ArrayCollection(['RK', 'BK', 'MK', 'AK', 'SK', 'JK']);

petNameList.dataProvider = new ArrayCollection([]);

</mx:Script>

<mx:HBox>

<mx:VBox>

<mx:Label text="Names List"/>

<mx:List id="nameList" allowMultipleSelection="true" dragEnabled="true"

dragMoveEnabled="true" dropEnabled="true" backgroundColor="yellow"/>

</mx:VBox>

<mx:VBox>

<mx:Label text="My Pet Name Is"/>

<mx:List id="petNameList" dropEnabled="true" dragMoveEnabled="true" dragEnabled="true" backgroundColor="yellow"/>

</mx:VBox>

</mx:HBox>

<mx:Button id="button1" label="Reset" click="initApp()"/>

Output:-

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