The plot thickens. Yes, holding the Ctrl key changes the behavior from a Move to a Copy. Based on your suggestion, I've delved into drag and drop and found that it's dependent on how the object is defined. Here's a relevant description from msdn: msdn link In particular, it has this description: As a result, I've looked at the functions in GuiRichEdit.au3. I can see where it does a GetDragDropEffect, but I can't see where it is ever set. I've never worked with objects beyond the simple e