Nginx transparent redirection to nextcloud folder

Hello,

In /etc/nginx/conf.d/MY.DOMAIN.d/ , I have added a file
sudo nano redirection.conf where I added

location / {

    location /documents {
        expires 1m;
        rewrite ^/(.*)$ https://nextcloud.MY.DOMAIN/s/rLxNwZQcxGKysi4 permanent;
    }
}

it does the job but is there anyway to have the same result but having a transparent redirection, keeping the url being https://MY.DOMAIN/docs (not becoming https://nextcloud.MY.DOMAIN/s/rLxNwZQcxGKysi4 in the browser) ?

Permanent redirect is certainly not working. Not sure about a temporary one, perhaps some browsers keep the original URL and just query the new one (did not check or test).
If you use proxy_pass, then you just proxy the connection through to Nextcloud. Then you probably have to go through the proxy settings in the Nextcloud config file.