This is a fantastic plugin, and it would be extremely helpful if it was possible to specify a list of specific post IDs to show, comma separated, i.e. only show these posts.
I will think about this idea... I don't want that widget form will have many options. It confuses new users of my plugin. Widget form must be very simple and understandable.
As workaround you can create new posts category, add needed posts to it and select that category in widget.