How to put custom buttons to manage listbox item(Move right/left,..etc) in between left and right ListBox in DualList box?

How to put custom buttons to manage listbox item(Move right/left,..etc) in between left and right ListBox in DualList box?

I'm using Bootstrap Duallistbox - v3.0.5 but I don't have any idea about how to put custom buttons controls in between left and right listbox for managing listitem's movement?