As this header is inserted by some javascript you should show it.
We have to know which css class is used.
I am rather sure that the class is not named "insertedheader".
Did you use something like this?
Code:
$(document).on('ready pjax:scriptcomplete',function(){
// Insert the column categories
$('#question{QID} table.subquestion-list thead tr:eq(0) td:eq(0)').remove();
$('#question{QID} table.subquestion-list thead').prepend('<tr class="ls-heading">\
<td rowspan="2" colspan="2"></td>\
<th class="answer-text inserted-header" colspan="3">Category 1</th>\
<th class="answer-text inserted-header" colspan="3">Category 2</th>\
</tr>');
Or something else?
But why do you insert something here? Isn't this sufficient?
To force the number into the next line insert a "<br/>" (not at all<br/>1)
Joffm