As Fig. B.1, but based on medium-resolution spectra. The plot shows the variability of the Hβ profiles over different years from 2015 to 2023. The mean profile based on 2015 spectra is plotted with a dashed line since the resolution in those spectra was lower. It also has the strongest emission contribution. The deepest blue wing absorption is seen in the mean profile from 2020 (dark green). However, also the 2022 profile (salmon) and the mean of the 2023 profiles (dark yellow) have a deep absorption in the blue wings.