if you’re primarily interested in “first for county”, then maybe there could be a feature request to optionally bring the Trends (and, specifically, the Discoveries) tab from the Taxa screen to Projects.
here’s a screenshot of what i’m talking about, with Discoveries at the bottom:
it should be technically feasible, since the discoveries tab data comes from an API endpoint that is not actually restricted by taxon. for example, if you wanted to see recent first identifications of species in VC-59 - South Lancashire, then you could sort of make that out from something like: https://jumear.github.io/stirfry/iNatAPIv1_identifications_recent_taxa.html?place_id=148989&per_page=30 .