When in “Photo library” view, right clicking on image and selecting the “Image properties” shows the properties in separate window. I would suggest to have an option to dock the property window on right or bottom side on the screen. This way it would not be somewhere over other pictures but organized.
Moreover, when it is shown now and you use alt-tab in Windows to get to another application, then back to PL and then you close the image property window the PL is hidden and the other app is shown. It seems like problem with main PL window getting focus.