There is no sample code for every pattern in the prototype applications as the circumstances which merit their use simply do not exist. You should be aware that the _cm_getInitialDataMultiple() method is only called once when the task is started and before the screen is displayed. It has one input argument called $fieldarray which initially contains any foreign key data which links it to the parent entity. This is also used as the output argument, so what you need to do is replace $fieldarray with a collection of as many rows as you like with whatever data you like.
How many rows you create in $fieldarray is entirely up to you. It may be a fixed number, or it may depend on the contents of another table.
function _cm_getInitialDataMultiple ($fieldarray)
$parent_data = $fieldarray;
$fieldarray = array(); // clear current data
// create initial data for first row
$row = $this->_cm_getInitialData($parent_data);
$row['field1'] = 'whatever';
$row['field2'] = 'whatever';
$fieldarray = $row;
} // while
} // _cm_getInitialDataMultiple