speech talking - 5th part of the shulchan aruch

there seems to be a saying by jews that there is a 5th part of the shulchan aruch (which is common sense) (i do not like this saying)

do/did any respectable Rabbis (Rebbes, Gedolay Hador, Talmiday Hachomim or Rabonim?) say or write this saying? (and by doing so made it a kosher saying)