Symmetric ACR families S₂, S₃, S₅, and S₆ in the 1:2:3 resonant chain for small-eccentricity configurations on (a) the (e₁ cos θ₁, e₂ cos θ₂) plane and (b) the (e₂ cos θ₂, e₃ cos θ₃) plane. The stable symmetric ACRs are in blue while the unstable ones in red. The notations of the families are the same as in Antoniadou & Voyatzis (2022), and the resonant angles of different configurations are presented in Table 1.