Hi Jason,
There may be another way to do this, but you can simply create a new Custom Menu Item, and simply follow the URI format of the TEC. First you would need to make sure that your Categories are properly setup; particularly in the Parent-Child way.
So to list your Sports(Parent)/Athletics(Child) monthly calendar, your link could point to:
http://example.com/events-view/category/sports/athletics/
or
For Sports Baseball:
http://example.com/events-view/category/sports/baseball/
and
To list all Sport in general:
http://example.com/events-view/category/sports/ (will list all children of sports: i.e. baseball, football, etc)
Hope that helps! 😉