I have found another way of opening two instances of PM6
Open PM6, double click on a folder full of images in the navigator sidebar, this will bring up the contact sheet of images
Double clicking on another folder will open a second copy of PM6 with both folders
Both copies have the two contact sheets showing
If I close the second contact sheet from the second instance it will close down altogether
The second contact sheet in the first copy is no longer showing
I hope you can follow that!