WordPress multisite information
siteID
This will include the ID of the currently shown blog in a WordPress Multisite environment.
siteName
This will include the name of the currently shown blog in a WordPress Multisite environment.
How is GTM4WP compatible with WordPress multisite instances?
GTM4WP can operate in WordPress multisite environments however there is no special treatment or option for them. You need to setup each site separately, a network wide option page is currently not available. You can however use some PHP constants to hard code the Google Tag Manager container code in wp-config.php and use this on each site in the network instead of setting this option one by one.