I would like to view both windows synchronised or parallellised (NO file transfer, only their display!):
- same sorting order in both windows, change one automatically changes the other accordingly;
- synchronised scrolling, i.e. always same file on same line in both windows;
- if a file exists on only one side, the other one should display an empty line.
Of course it should be the user's choice whether (s)he wants to enable this or not.