A Cinema 4D C.O.F.F.E.E. script that adds an expresso tag to a selected object.

addCompositing.CSC

main(doc,op)
{
  // Insert a expresso tag on the selected object
  if (!op)
    return NULL;

  var expressoTag = AllocTag(Texpresso);
  op->InsertTag(expressoTag);
}