In addition to the normal zoom tools, SpaceMonger also remembers what you've looked at recently: when and where you zoomed in, when and where you zoomed out, and when and where you panned the display with the scrollbars.
If you want to go back to a previous zoom/pan position,
simply click the zoom-back tool:
This tool will jump back through the last 100 positions you were at.
If you go back too far, or you want to jump back and forth between two
positions, you can use the zoom-forward tool:
This tool will return you forward through the list of positions you've viewed.