Thanks for chiming in @deboas @kiwifergus @heyitshelios @charlie. Another use case for checkmarks is this proposal by @joeysantore / @jdmore. I don’t know if this would be doable, given the database structure, but I can definitely see myself perusing checkmark icons in the taxonomy view for a given genus to see which species I’ve previously observed or have yet to observe.
I also like a lot the suggestion that such a checkmark icon could act as a universal UI element within iNat pointing to one’s list observations for that taxon.