Is there software or a device that allows bookmarking positions to allow variation analysis? I'm wondering if there is any chess software or portable chess computer that allows a position to be bookmarked while a variation is examined?
For example, it's possible to download pgn for games analyzed in Chernev's logical chess. However, there isn't a diagram for every position, and occasionally the author outlines alternate moves and their consequences. While it's possible to follow through this analysis on a board and "unplay" the moves back to the point where this divergence from the actual game takes place, this can be time-consuming. What I'm looking for is the opportunity to bookmark a point in the game, follow the variation through, and then click back to the bookmark to continue on with the game, rather than clicking a back arrow for every move that was made.
Thanks
Chessbase is a commercial product that solves your problem.  Any position in Chessbase is in essence a bookmark.  You can just click on the move/position you want to go back to (all the moves are available visually beside the chess board).  I believe the same functionality is available for free with Scid.