library opened as a separate window does not remember it's position on a secondary monitor
it seems to know the position -- but it jumps to that same position on the main display instead.
- open project
- open prefs
- choose "same as before" in prefs for how to open the library -- make sure "close" is unchecked
- open library as separate window by clicking the window button
- drag to secondary display
- quit
- open the same project.
The window appears in the main window. On my setup the window is positioned on the far side of the main display -- which is the same edge of the main display as the window was positioned on the secondary display. This seems to imply that it's remembering its pixel coordinate -- but not with reference to the secondary display.