By default the main window is split into three vertical panes (see below).
In the left pane, the Operations view , showing the operations whose preconditions and guards are true in this state (the view also uses a blue circular arrow icon when an operation does not change the state);
In the middle the State View, containing the current state of the B machine, listing e.g., the current values of the machine variables;
In the right pane there are a variety of subviews, which can be activate: