3 monitors. Laid out as 2, 1, 3 left to right. Middle monitor (#1) is the main display.
Layout launches in middle monitor.
If there has been a change to the SU model associated with the Layout file, the document setup window always launches in the left monitor (#2, in this instance).
Document setup should always open in the same monitor as Layout. In lieu of that, it should open in the last place it was anchored. I have to move it into my work area focus every time and it’s a PITA.