  In [Dugan-Glennon-Gunnells-Steingrimsson-2019], the authors introduce tiered
trees to define combinatorial objects counting absolutely indecomposable
representations of certain quivers, and torus orbits on certain homogeneous
varieties. In this paper, we use Theta operators, introduced in
[D'Adderio-Iraci-VandenWyngaerd-Theta-2021], to give a symmetric function
formula that enumerates these trees. We then formulate a general conjecture
that extends this result, a special case of which might give some insight about
how to formulate a unified Delta conjecture [Haglund-Remmel-Wilson-2018].
