Grouping on a child field

I figured out how to build an employee churn report using a metrics table that's a parent of my employee table and formula queries (thanks quickbasejunkie!) but am stumped on how do grouping or filters based on a multi-select list on the employee table. 

For additional context, the churn report currently shows me the whole company's churn result by month, but I need to group it by team. My team leaders just see their team's results because I have their access to the employee table tuned - but I don't have an overview. 

thanks in advance!