Mobile devices have the ability to have different functions assigned to certain buttons
called soft keys. WML allows you to assign certain functions to them.
You must have created a paragraph in the card to create a soft key in.
Select paragraph (shown as p0, figure below) and press do element button to create new do element.
Click on attribute type and select value from the drop-down menu one of the known types or enter new one. Certain keys are standard on most phones (like prev and accept), while others may not be available on some models.
Assign value to label attribute.
Assign an action for the do element by pressing one of the element buttons: