The Shift buttons move the view along the nominated axis, allowing you to centre the focus of your interest. It's not quite as simple as saying they move the view 'left' or 'right', since the various panes show different the axes are different angles. The best way to understand how they work is just to experiment with them to see the effect.
The Reset button returns the view to the default position.
Note: After a simulation has been running for a while, pressing any of these buttons will result in a dialog box asking you how you want to redraw trails at the new scale. Gravitorium remembers up to the last 4096 positions where each body was located, so a full redraw can take some time, particularly if there are many bodies in your system. The advantage is that you don't lose your impression of what is going on when you zoom in and out.
However, if you are doing a lot of small moves, the dialog box can get pretty annonying. It's therefore best to adjust the view early on before you have too many trail points recorded.