To enable Multisite without the plugin, connect to your site using a FTP client or cPanel file manager, and open the wp-config.php file for editing.

You need to add the following code to your wp-config.php file just before the /* That’s all, stop editing! Happy blogging. / line. / Multisite */ define( 'WP_ALLOW_MULTISITE', true ); Once you are done, you can save and upload your wp-config.php file back to the server.

This code simply enables the multisite feature on your WordPress site. Once enabled, you will still need to setup the multisite network.

Sorry for inconvenience caused and you are looking for multi network feature without plugin so you need to do some stuff on code to access sub sites:

// Multisite define( 'MULTISITE', true );

define( 'SUBDOMAIN_INSTALL', false );

define( 'PATH_CURRENT_SITE', '/' );

define( 'DOMAIN_CURRENT_SITE', $_SERVER['HTTP_HOST'] );

// Likely not needed anymore (your config may vary) //define( 'SITE_ID_CURRENT_SITE', 1 );

//define( 'BLOG_ID_CURRENT_SITE', 1 );

// Uncomment and change to a URL to funnel no-site-found requests to //define( 'NOBLOGREDIRECT', '/404/' );

/**

• These are purposely set for maximum compliance with multisite and
• multinetwork. Your config may vary.

*/ define( 'WP_HOME', 'http://' . $_SERVER['HTTP_HOST'] );

define( 'WP_SITEURL', 'http://' . $_SERVER['HTTP_HOST'] );

For maximum flexibility, use something like this above