Where in /em or /console or /analytics can I find info on currently connected OAS users ?
Under Console > Session and Query Cache.
Locate the Sessions sections.
The Sessions section at the top of the page shows how many users are currently signed in
@Mr. C - You can see how many users are signed in to your service and view detailed information about each user from the Manage Session page. Please refer the below document for more details and navigation.
Reference:
https://docs.oracle.com/en/cloud/paas/analytics-cloud/acabi/monitor-users-and-activity-logs.html