Where is the Deleted Task List?

Welcome, @Genevieve_V,

Your best bet currently is to use Advanced Search (available on any paid plan), but you can save (Star) the search to make it appear in your left sidebar for easy re-use. See this great post by @Richard_Sather for details and also the whole thread its in:

Asana is evolving very quickly these days with many new features and A/B tests running. It’s not clear, but I would guess that Asana would want to make the ability to retrieve deleted items more discoverable in the future, as it was in the past, but that’s just conjecture.