This display element is used to display a button on the screen.
The displayed text within the button will be the model's name (e.g. if the Button model is named "Submit", the text Submit is displayed).
While any other display element may contain an action sub-model named <On Click> to model what should be done if the user selects the displayed data, the raison d'etre of a button is to allow the user to press it.
Therefore, there is no need to add an <On Click> sub-model and model a process within it. Rather, model the required process directly within the Button model itself (as if it were an action model and not a display model).
You can also add a Popup element in case pressing the button should open a popup on the screen.