This is part of the customization code which does something similar to what you want to achieve:
// move text from column B to column A and
// empty columns B through E
var copyPaste = $('row:eq(-2) c[r^="B"] t', sheet).text();
$('row:eq(-2) c[r^="A"] t', sheet).text(copyPaste);
var emptyCellCols = ['B', 'C', 'D', 'E'];
for ( i=0; i < emptyCellCols.length; i++ ) {
$('row:eq(-2) c[r^='+emptyCellCols[i]+']', sheet).text('');
}
Answers
Here is something on copying and pasting content - and many other things regarding Excel export customization.
https://datatables.net/forums/discussion/45846/datatable-excel-export-how-can-we-apply-multiple-styles-to-same-cell/p1
This is part of the customization code which does something similar to what you want to achieve: