Add option value for quick search – Jobs Blue

I have this Jobs Blue as a child theme on my page. There is a quick search panel on the page which I’d like to modify a little bit.
I’m trying to add at least one more value in to the “all position type” selection, for example “thesis”. Since I found this CUSTOMFIELD_LIST(‘jobtype’,””,”author”), I modified the “_language.php” of Responsive Job Board Theme to add this “thesiswork” in it, as in the attached file, but that doesn’t to be working.
What should i do to add one more option value into this quick search, not the advance search ?
Regards.