It appears the feature is in mantis now: 0003174: New feature-Play all videos inside folder without need to create playlist - MediaPortal Bugtracker
I was going to ask: the play list will include all files in the folder and the tree of child subfolders, right? I have a folder called "home videos" and a set of subfolders for each year: 2010, 2009, 2008, 2007 and so on. I want a random play, but I don't want to move all the files into one parent folder.