sometimes, when one has multiple items of the same type and wants to split the stack to specific amounts, it is useful to be able to rightclick on a stack to add a single piece of the item held. With enderchests it causes the enderchest stack to go into the enderchest inventory, which (though working as intended) isn't the wanted behaviour most users would want.

Hmm, i mean, would it be possible to make it so that if one maybe shift-rightclick's it spits out/takes in one item at a time?