D+E
Let $Pic(\bar{M}_{0,n})_Q^{S_n}$ denote the vector space of $S_n$-invariant divisors with rational coefficients. Here, given two $S_n$ symmetric $Q$-divisors $D$ and $E$ on $\bar{M}_{0,n}$, the function returns $D+E$.
i1 : D=symmetricDivisorM0nbar(6,{1/2,1/3}) 1 1 o1 = -*B + -*B 2 2 3 3 o1 : S_6-symmetric divisor on M-0-6-bar
i2 : E=symmetricDivisorM0nbar(6,2*B_2+3*B_3) o2 = 2*B + 3*B 2 3 o2 : S_6-symmetric divisor on M-0-6-bar
i3 : D+E 5 10 o3 = -*B + --*B 2 2 3 3 o3 : S_6-symmetric divisor on M-0-6-bar