I tried below but it does not adjust the column width. Any other idea?
my column name is Progress (internal name is Progress as well) and it's multi-line type field.
Try the below code in a content/script editor webpart. Change the name of the column. I see the max-width of the column is set to 500px. So if you want to make your column width more than 500px, then you have to change the max-width, otherwise that is not needed. I ran this code on SharePoint online and it worked fine.
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js" type="text/javascript"></script>
<script type='text/javascript'>
$(document).ready(function(){
var columnName = 'Progress';
var element = $("div[name='" + columnName + "']").parent();
var width = '600px';
element.css('max-width', width);
element.css('width', width)
});
</script>
The script below did not work either.
<style>
/* new class created */
.ms-longg
{
width:500px
}
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js" type="text/javascript"></script>
<script type="text/javascript">
$(document).ready(function(){
//removed existing class
$('input[title="Progress"]').removeClass('ms-long');
//add New class for that textbox
$('input[title="Progress"]').addClass('ms-longg');
});
</script>