the real trick is to let BLIde know wich parser it has to activate for any unknown extension (by default it uses the txt parser, but it would be great to tell BLIde that (in example) files with extension .myprefs uses the XML parser)
In my experience with XML 90+% of files have a header at the top that identifies them as XML files. Here's the only 3 variations I found in about 30 files picked at random from a .xml system search. The header being the first line of text at the top of the page.
Either:
<?xml version="1.0" ?>
<?xml version="1.0" encoding="utf-8"?>
<?xml version="1.0"?><CERTIFICATECHAIN><CERTIFICATE>P