I am looking for the name of the box in the Box Language of Mma making integrals, such as those shown in the image below as well as of the sign of the partial derivative. I understand that I can get it through MakeBoxes trick, but it would be nicer to have special operator for such a purpose. The code with such an operator will be more concise.
It seems that there are no special boxes for these symbols. One can, however, use standard operators of the box language and insert there symbols from the palette Menu/Palettes/Special Characters/Symbols such as integral or partial derivativederivative. Like this one finds:
Otherwise, one can do this:
with the same effect. This, for instance,
returns a partial derivative