I have a dev server on 8.1.36, and that tag is still there.
You can get designer info from system.util.getSessionInfo, e.g.
addresses = [s['address'] for s in system.util.getSessionInfo() if s['isDesigner']]
print addresses
print len(addresses)
But it sounds like this would be better for your use case
Get current scope in scripting - General Discussion - Inductive Automation Forum