Welcome to the forum!
I’m not totally sure I understand what you want to see – are you looking for a set of observations or a set of taxa? That is, if there are 3 observations of Carex pensylvanica and 2 observations of Carex albicans, do you want to see 5 observations or a list of 2 species?
Some examples of what you can do –
If you want to see all observations within Section Acrocystis in the US (identified at any rank), put Acrocystis in the taxon box and USA in the location:
If you want to see the list of species within Section Acrocystis with observations in the US, click the tab that says 26 to get this:
One thing you can’t do in Explore is return all observations in genus Carex, sorted by Section. That has been requested before and you can add a Like to the post to show your support.