The ideal situation maybe that a GM has everything entered into his copy of RW prior to a game and clicks the reveal icons flawlessly during play, but I know there will be any number of instances where some bit of information is revealed during my game that doesn't yet exist as a snippet (quite possibly because I or one of my players has just invented it on the spot) or I'm too into the game to remember to pull up the appropriate topic and click the orb -- and all of that is assuming that I remember to bring my laptop to the game in the first place!
To effectively leverage the Game Session feature, it would be nice to be able to edit the reveal datestamp (presumably with something like a right-click in the Reveal History pane) so that the reveal can retroactively appear when filtering for the appropriate game session.