When you place controls in a window, PowerBuilder assigns them a default tab order, the default sequence in which focus moves from control to control when the user presses the Tab key.
Tab order in user objects
When the user tabs to a custom user object in a window and
then presses the Tab key, focus moves to the next control in the
tab order for the user object. After the user tabs to all the controls
in the tab order for the user object, focus moves to the next control
in the window tab order.