\N is a default message code. it should be compatible by default - if it is not, then you have something in your scripts that prevents this from working.
No, it is not a default for custom scripts, especially because the default engine got no name box at all.
Khas' script uses
draw_text not
draw_text_ex, and only the latter supports these message codes.
Also, an equally important fact is that Khas' script uses sprites and not windows to make these text boxes, which means there is no
draw_text_ex method to be used on these objects.
Reading the description of the script (which is surprisingly short), it seems that there is a new message code that should change the text in the namebox:
Use this instead of the \N version.