Optical-to-NIR (Gaia DR2 – 2MASS) CMD of the objects in our spectroscopic sample: red squares = previously known WDs (including two rejected), black lozenges = new WD candidates (confirmed and rejected), blue crosses = hot subdwarfs (sdO and sdB), green dots = all remaining stars (mainly representing FGK subdwarfs). New WDs and candidates, rejected known WDs, and one known WD binary are marked by their CA numbers. The dashed line corresponds to one of two colour-magnitude limits for WDs used in Scholz et al. (2018).