Evolution of line velocities of in the four subtypes of SESNe. In each figure, different subtypes are plotted in distinct colors: green–IIb, blue–Ib, magenta–Ic, orange–Ic-BL. The same supernovae are plotted with symbols shown in the top legend and connected by lines. SN 2016coi and SN 2019ehk are represented in red and cyan, respectively, as their spectral phenotypes differ from the four subclasses.