Already since the first version in June 2004 Chess Position Trainer offers a unique position tree view of your repertoire in a separate window which has been much improved with version 4. You can expand or close any node. If you click on a node the corresponding position is shown on the board.
If you move your mouse over a specific move notation and wait for a second a preview with a chessboard shows the corresponding position. This way you can remain at the current position on the main chessboard, which makes it very easy to quickly browse through your opening in an alternative way.