Tools:
Nginx 1.15.5
PHP 7.3 (7.3.0RC4) VC15 x64 Thread Safe
Xdebug 2.7.0beta1 - PHP 7.3 VC15 TS (64 bit)
PHPStorm 2018.1.6 (Build #PS-181.5281.35, built on June 14, 2018)
Windows 8.1

nginx.conf

worker_processes 1;
error_log logs/error.log notice;
pid logs/nginx.pid;
events {
worker_connections 1024;
}

http {
include mime.types;
default_type application/octet-stream;
sendfile on;
keepalive_timeout 65;
proxy_buffer_size 128k;
proxy_buffers 4 256k;
proxy_busy_buffers_size 256k;
fastcgi_buffer_size 128k;
fastcgi_buffers 4 256k;
fastcgi_busy_buffers_size 256k;
fastcgi_read_timeout 300;

server {
    listen       80;
    server_name  localhost xxx.local www.xxx.local;
    access_log  logs/access.xxx.local.log  combined;
    error_log  logs/error.xxx.local.log  notice;
    root   "d:/xxx/src/web";
    index index.php index.html;
    location / {
        root   "d:/xxx/src/web";
        index index.php index.html;
        try_files $uri $uri/ /index.php;
    }
    location ~ \.php$ {
        root   "d:/xxx/src/web";
        include        C:/programs/nginx-1.15.5/conf/fastcgi.conf;
        fastcgi_pass   127.0.0.1:9123;
        fastcgi_index  index.php;
        fastcgi_param  SCRIPT_FILENAME 

$document_root$fastcgi_script_name;
}
}
}

XDebug config in attached php.ini file