[S]zonsui is a system variable (alpha) that can be used in classic X3 functions to specify the order in which fields should be accessed. This is especially useful in ADC functions to redirect users to the desired fields.
If no value, then the supervisor goes to the next field based on the order on the screen.
$OK # After OK, Redirect to first field YFROMIDENT [S]zonsui = "[M:XASC]YFROMIDENT" End
Can be used to stay on the current field without triggering a blocking message (in ADC for instance).