HSM behavior data file is created and modified with the LabHSM Editor. The main screen of the editor is shown below.  

LabHSM Editor Main Screen.

Despite statecharts were developed as a graphical formalism, the state structure of an HSM is just a tree, so it can be suitably depicted with just a tree control. The State control allows selecting a current state. The currently selected state can then be dragged within the state control to another position, deleted, renamed, set as default, or a substate can be added to it. Entry and Exit actions can be assigned to the state in the respective controls. The right part of the screen provides access to an array of transitions for the selected state. Transition information consists of the Target State, Transition Type, Event that triggers the transition, its priority, a list of Event Handling Actions, and an Override Flag.
 

In the presence of behavior inheritance, the concept of To (Deep) History transitions, possible entry and exit actions for states positioned at different levels of hierarchy, determining the actual target state and the full list of the actions that must run in a particular transition becomes nothing but trivial. It is all handled automatically, partially by the LabHSM editor when saving HSM file, partially – by the Run State Machine action at run time. However, the developer sometimes will want to make sure at design time that the HSM will run exactly the actions he expects it to run and will end up in the state he expects it to. For this purpose, the LabHSM Editor is equipped with the What If…? Screen shown below.

LabHSM Editor What If...? Screen.

It allows entering a source state, choosing an event, and the latest active substate of the target state (if applicable). Then the editor (based also on what was entered in the main screen, of course) will show which state will become the actual target state and the full list of the transition actions.