Mixed-charge ($\pm\pm\pm\mp$) four-pion correlations versus $Q_4$ in pp, p--Pb, and Pb--Pb. The full ($C_4^{\rm QS}$), partial cumulant ($a_4^{\rm QS}$), and cumulant ($c_4^{\rm QS}$) correlation functions are shown. The inset figure shows a zoom of $c_4^{\rm QS}$. Systematic uncertainties are shown by the shaded bands. Low and high $K_{\rm T4}$ quadruplets are shown. The average of the charge conjugated correlation functions is shown.