Window.DefaultLocation

From Xojo Documentation

Property (As Window.Locations )
aWindow.DefaultLocation = newWindow.LocationsValue
or
Window.LocationsValue = aWindow.DefaultLocation

New in 2019r2

Supported for all project types and targets.

If it's a Document window, this property represents the window's location at which the window will initially be placed when it opens.

Notes

The Window.Locations enumeration contains all potential values for this property.