I would like to run aggregation pipeline commands against a database.  Specifically, I will want to build a pipeline where a step includes executing $currentOp on the admin database to gather running and dormant processes.

The Compass application does not present the aggregation pipeline builder UI until after a collection is selected in scope.  This leads to the stage not executing on the admin database and instead presenting an error message:
$currentOp must be run against the 'admin' database with {aggregate: 1}