adverb/ˌkomo ˌkjen ˌno ˌkjeɾe la ˈkosa/
just like that; as if it were nothing; without a care in the world; on the Q.T.
“El Señor, de rato en rato, metía la mano en la manga y llevaba a la boca una cereza; y como quien no quiere la cosa, al descuido y con cuidado dejaba caer otra, que San Pedro sin hacerse el remolón se agachaba a recoger, engulléndosela en el acto.” — Every so often The Lord put his hand up his sleeve and brought out a cherry to eat, and without a care in the world, accidentally or on purpose, would drop another on the ground, which Saint Peter, without idleness, would bend down to scoop up and eat.
Literally, “like someone who doesn't want the thing”. Compare Portuguese como quem não quer a coisa.