The toolbar offers functions for use while playing a game.
If the loaded levels are grouped into level collections (e.g. the default levels), then you can select between the different collections with game chooser on the left of the toolbar.
The Prev and Next buttons moves between different levels. These functions are also available by typing Alt-P and Alt-N.
The Reset button restarts the current level. This function is also available by typing Alt-R.
The Undo button allows you to undo the last action performed in a level. This function is also available by typing Alt-U.