[ubuntu] Move the position of the opened apps in the taskbar with the mouse or keyboard

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http://ubuntuforums.org – Hi, is there any desktop environment, windows manager or fork of ubuntu 12.04 that permits moving the apps in the taskbar (traditional taskbar, not unity left panel)???? You know, for example in Firefox I can change the position of the tabs. I would like to do the same for the apps in the taskbar. I tried xfce, but it doesnt work.. (Hardware)