Another thing you can use to try and find unobserved taxa is the compare lists tool. You start at :
https://www.inaturalist.org/observations/compare
And then gradually fill in the 2 query boxes with the parameters from a search. It’s experimental/not supported. Anything beyond 500 taxa causes it to perform inconsistenty, so you must filter down to that.
So for example in Query 1 having taxon_id=47224&place_id=18 an in query 2 having taxon_id=47224&place_id=2993 will compare the list of butterflies (taxa 47224) reported from the state of Texas vs Tyler county.
The way to read it is the numbers are the total observations reported. So for example 1562 Eastern Giant Swallowtail records in Texas, but none in Tyler county.
You can click the not in common to see all the ones with no Tyler records.
You mention being mostly interested in plants, obviously that will exceed the 500 taxa, so you can do this if you filter down to family etc