Overview of all the clusters from our k-means model. The solid lines represent the cluster centres of the respective clusters. The shaded areas represent the spectral line density within each cluster, where a stronger colour means a higher density; red and blue represent QSEBs, where the cluster centres in the red group have ${\overline{I}}_{{\lambda }_{\text{iw}}}>{\overline{I}}_{{\lambda }_{\text{ow}}}$ in both wings, while the cluster centres in the blue group have ${\overline{I}}_{{\lambda }_{\text{iw}}}>{\overline{I}}_{{\lambda }_{\text{ow}}}$ in only the blue wing; orange represents clusters containing both QSEB and non-QSEB profiles; purple represents clusters with MCs; grey represents clusters with neither QSEBs nor MCs; the dotted line is the spectral profile that deviates the most from its cluster centre; the dashed line is the background profile, which is the average profile over the entire dataset and serves as a reference; n represents the fraction of pixels from the entire dataset (N = 685 ⋅ 10⁶ pixels) within the respective cluster centre. I_wing is the average intensity of the second to outermost wavelength points in the blue and red wing (we did not choose the outermost wavelength points to avoid blends).