I have a solution that is designed to occasionally call a New Window that shows its Close button, but with a caveat. The script that calls that window (a Document style window) initially calls a user abort script that does this:
If [ Get ( CurrentPrivilegeSetName ) = "[Full Access]" ]
Allow User Abort [ On ]
Allow User Abort [ Off ]
That window later is placed in an indefinite pause state that is broken by pressing a button that performs some things that must be performed before that window closes. This button then closes the window.
In the above scenario, the user has never been able to close that window by pressing the close button in the title bar (the red button on the Mac and the X on Windows); they could only close it by pressing the button I provided them. This has been true with FM 15 on both Mac and Windows 8. Only a Full Access user could use that title bar close button in such a situation.
Now I notice that, though this still works like that on the Mac with FM 16, it doesn't work like that in Windows 10 with FM 16. Instead, the user can now close such a window with the title bar close button (the X).
It looks like I now must hide the title bar close button to keep the user from closing the window like this.