Add Item Dropdown-menu action

Hello all,

I was wondering what I would have to do to create a extra item-option shown in the dropdown menu under each thumbnail. What I am trying to do is make an option for users to Copy a certain item to a pre-defined folder (this is a folder used by a java slideshow on another site). I dont know exactly where to find the code that is associated with the dropdown menu of an item, maybe you guys could give me a hint what to do.

Greetings,

XiS