This is so close now. The following groups them properly by weekday but it doesn't sort the weekdays into order:
index="windows" eventtype=winregistry_windows registry_value_name=viewclient_broker_remote_ip_address registry_key_name="volatile environment" registry_value_data="*" | eval weekday=strftime(_time, "%A") | chart count by weekday, CPS
So I tried this one but I think, because I"me using chart, the sort_field field isn't ending up in the cart to be able to be sorted on. If I change it to chart count by sort_field then it works (so the fields are being created properly) but then of course I get numbers 1 to 7 instead of the days of the week...
index="windows" eventtype=winregistry_windows registry_value_name=viewclient_broker_remote_ip_address registry_key_name="volatile environment" registry_value_data="*" | eval weekday=strftime(_time, "%A") | eval sort_field=case(weekday=="Monday",1, weekday =="Tuesday",2, weekday =="Wednesday",3, weekday =="Thursday",4, weekday =="Friday",5, weekday =="Saturday",6, weekday =="Sunday",7) | chart count by weekday, CPS usenull=false | sort by sort_field
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