By the looks of things if you setup global connection "remote display number" and preset a display to be a On Top screen then when you call the display number it will pop up.
Then reset the remote display number to 0 otherwise the operator wont be able to change screens, then after a PLC timer set the Close all popups to hide the screen again.
I will try this, hopefully later this week and report back once I have tested it unless someone already knows this doesn't work