The Delta Conjecture, valley version

Let $n$ be a positive integer and let $k$ satisfy $k\leq n$. Let $\mathcal{M P F}_{n,k}$ be the set of valley-marked parking functions of size $n$ with $k$ marked valleys and labels $[n]$. For such a parking function, let $\operatorname{area}$, $\operatorname{dinv}$, and $\operatorname{ides}$ denote its area, marked diagonal-inversion, and inverse-descent statistics, respectively. Let $e_n$ be the elementary symmetric function, let $\Delta'_{e_{n-k-1}}$ denote the primed Delta operator indexed by $e_{n-k-1}$, and let $F_{\operatorname{ides}}$ be the fundamental quasisymmetric function indexed by the inverse-descent set. The Delta Conjecture, valley version. For all $k\leq n$,

$$\Delta'_{e_{n-k-1}}e_n=\sum_{M P F\in\mathcal{M P F}_{n,k}}t^{\operatorname{area}(M P F)}q^{\operatorname{dinv}(M P F)}F_{\operatorname{ides}(M P F)}.$$

This is one of the principal combinatorial formulations of the Delta Conjecture; the case $z=0$ recovers the Shuffle Theorem. Many special cases have been proved, but the general conjecture remains open.