The Y/C shift filter is a fliter that allows to apply a shift between the luminance and the chrominance in the picture.

Note that the chroma filter (other filter provided with DScaler) is doing something similar.

The Y/C shift filter works on the input fields and apply the shift to the luminance relative to the chrominance. Compared to the Chroma filter, its advantages are to allow a shift of several pixels and to requires less CPU. Its disadvantages are to allow only a horizontal shift while the Chroma filter can work in two directions, and to work on luminance while the Chroma filter works on the chrominance (the human eye is more sensitive to the luminance information than the chrominance information).