Yes Yes Yes Yes and Yes. Been banging on about this for a while. This should be for all items and maybe as opposed to "right click" could use "middle mouse button" since it's not used for anything anyway. (Pressing down the scroll wheel for those who don't know what middle mouse button is)
That or just make it bindable so people can choose their own?
can we also have double click to take the whole amount while we are there? like i want to move 40 iron ingots from my inventory to my friends? double click the 40 and drag to the give button (so that the number 40 populates in the field).