Misfire at idle only, worse in the cold

nothing new at work to help ya out, sorry.
but fuel trims basically show how rich and lean a car is running. short term reacts quickly, long term reacts to short term and vice versa. they try to meet in the middle with a number around zero, negative being the lean side and positive being the rich side iirc

on a scanner it will probably show up as ltft and stft (log term fuel trim and short term fuel trim)
they can give you a half ass idea of whether or not your car is runnign rich/lean/stoich