Open Pop up window for a tag change on only one or more specific clients

How can I open a pop up window on only one or more specific client sessions for an event, (on specific user client like operator/manager)?

Depending on how you open the window.
You could either using the security tab and only enable/visible to certain logged in users.
Or in a script check the username or group before opening the window

Get logged in user name:
system.user.getUser

Get logged in users role(s)/group(s):
system.user.getRoles

if event.propertyName == 'dtEvent':
if event.newValue == 1:
if "Operator" in system.security.getRoles():
#show popup
window = system.nav.openWindowInstance('pop up')
system.nav.centerWindow(window)
pass

I am doing this on the window I want the pop up to be, But All my pop up instances are docked in the center of the client and are exactly on the top of each other.

How can I make them appear random and movable/dragable!

Instead of calling centerWindow, use the window’s reshape() method. You’ll have to compute the coordinates you want from the previous window’s coordinates.

The coordinate system for all windows is the undocked area of the client desktop. Windows are not connected to each other based on what opens them. You have to script whatever “connection” you want.