Add global variables (i.e. for path)

I tried setting global variables for the path and filename, e.g. path=path\to\save\files\{category}\ and filename={appname:regexreplace:([\s\t\r\n\&]+): } {version}.{url:ext} but variables inside of variables don't seem to work, and everything is taken literally. It would be great if this could work, since then if it ever needed to be changed it could just be changed there and that would affect everything, but I've tried escaping the braces and it doesn't help. This would be very useful to allow the path to be changed in the main settings and have it affect all applications without having to go through and change each one individually.