Constant Neutral Loss (CNL) scans are supported via Skyline's
Spectrum Filter feature. In CNL data the mass spec is programmed such that Q1 and Q3 operate in concert to record only Q1 values for which a corresponding Q3 value is detected with the desired loss or gain of interest. You may be interested in several different losses (or gains) for a given precursor m/z, and Skyline provides for this by letting you set up multiple precursor targets with identical m/z but different neutral loss values in their Spectrum Filters.