The thing is my script has to write things to a folder that doesn't exist and I don't know how to change it to not use the default directory. So i want to use change the default directory (...)
You may create a subdirectory to load/safe data to...
For example, ".mkdir $+($mircdir,myaddon)" will create a \myaddon folder at the $mircdir location if he does not exist already, and whatever the $mircdir for your mirc - or someone else using that script - is.
Now you can direct your read/write routines to that directory, e.g. "write $qt($+($mircdir,myaddon\,myfile.txt)) sometext". I used $qt() to enclose the path to myfile.txt with quotation marks, due to possible spaces in path or filename.