Currently we are unable to choose custom Regions such as creating a Western Palearctic list to then pick from countries visited to show a Life List for this for example that can also be shown in Graphs on checklists or Country lists.
Related to this is the current limitations to only pick from a single visited site to see total species seen, but this doesn't scale with likes of United States where the Outer Lying Islands of USA form one of the US States but you cant choose from a list of multiple countries.(I think from Memory that Mexico is considered a US State in BJ which is actually Central America)