This operator is only available when connected to an Aster database.
The Lpad operator prepends a character argument to a string argument up to the length of argument number three. If the string is already longer than the length argument, then the string is truncated to that length (from the right). When dragging an Lpad operator into a variable, the following tree element is created.
Variable Creation > Input > Variables: SQL Elements pane - String Functions > Lpad