please refer to screen shot first : http://yunpan.cn/Q4B2Wwqtc6qth
To get left-positioned panel I need to add panel 3 times by 'right click on desktop -> Add panel', then u need to remove the other two panels.
can we add panel on left/right/top/bottom more easily ?

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Yes, you can. First, add a panel as you normally would. Then click the cashew on the panel - which will cause the panel controller to appear. If you click and drag on the controller, it will allow you to move the panel to a different side of the screen.