DesktopWindow.HasCloseButton
From Xojo Documentation
Read-Only Property (As Boolean )
BooleanValue = aDesktopWindow.HasCloseButton
New in 2021r3
Supported for all project types and targets.
New in 2021r3
Supported for all project types and targets.
If True, the window will include a Close button in its Title Bar.
Notes
On macOS, if the ContentsChanged property is True, then the close button will display a dot, which is used to indicate there are unsaved changes in the window.
MacOS does not display close buttons on Movable Modal windows.