under Apache I can set the index very easy. Like:
How can I set this in nginx?
I had tried: index index.php?parameter=xyz but I get an 403 error.
In nginx, options for index are files. But I think you can try:
If it does not work, why don't just use
I'm not sure if this is what you are looking for, but its practically an API:
Obviously those examples are for the try_files, but parameters would be the same passed in. This is just an example where they are used.