First you would want to key off an event such as the "Add" button click event so you would start with:

$(document).on('click', 'a.cf-table-add-row', function(e) {
   
});

(note: this works with one table on the form. If you have more you will need to add a class to the table and reference it before the anchor tag in the above query)

Now this is usually a matter of preference, but I always add a class to my table so I can query it in code.

$(document).on('click', 'a.cf-table-add-row', function(e) {
   var _this = $('li[attr=tableclassassigned] tbody tr:last'),
       _prev = _this.prev(),
});

That next line gives you access to the row previous to the row that was just added. At this point, you can then reference each of the table row fields. Again, you will want to give each field a class name so you can reference it in a query.

$(document).on('click', 'a.cf-table-add-row', function(e) {
   if (!$('#idofcheckbox').prop('checked')) return;
   var _this = $('li[attr=tableclassassigned] tbody tr:last'),
         _prev = _this.prev(),
         _field1 = _prev.find('td.classassignedtofield input.singleline').val(),
         _field2 = _prev.find('td.classassignedtofield2 input.singleline').val();
   _this.find('td.classassignedtofield input.singleline').val(_field1);
   _this.find('td.classassignedtofield2 input.singleline').val(_field2);
});

The above code should get you what you are after once you assign the class names to the table and fields.