Trimble Knows Door Combination is a written note found in The Brigmore Witches.
Gone to look into the water flow situation in the sewers. lf you need access to the engine room while I'm away, talk to Nurse Trimble. He's the only other person with the door combination.
It can be found in the Drapers Ward Textile Mill next to the door to the engine room during the mission The Dead Eels.