How can I get the named parameter that was used in the query?

How can I get the named parameter that was used in the query ?
for example, is somebody issues a query
SELECT * from employees where name=$EmployeeName
and give "EmployeeName " as a named parameter, how can I get the details of that parameter from somewhere like system:completed_requests or prepareds ?

By default those will not be tracked. One can enable by cc @Marco_Greco