Hello! o)
While talking about the ontop-button-editor thing, I recalled a wish that almost always comes up whenever I start customizing toolbars/buttons.
It happens regularly that I have a path in the clipboard or a piece of code for a new but very similar button, so I rush into customize and realize.. hmm, I cannot create a copy of an existing button without loosing what's in the clipboard right now. So I wish there was a simple "Duplicate" functionality for buttons and menu entrys, which does not destroy what I have in the clipboard. Currently I need to cancel my initial action, copy & paste the button first, leave customize mode, get back to where I copied what I already had in the clipboard before, copy that again, re-enter customize mode and finally get the content pasted into the new button, menu entry etc.
EDIT: Checking twice before posting I realize I can hold CTRL to create a duplicate by dragging the item by mouse. Not bad! o)
I guess a "Duplicate" menu entry still makes sense, as it's more straightforward for everyone, thinking about newbies as well as long time users like me! o)