Removes this server from a network. network_id is the full Network ID, as shown by /group-admin network list. By default Discord shows the /group-admin commands only to members with Manage Server.
Anything that is not a complete Network ID is refused with That doesn't look like a Network ID. If the server was in the network the reply is Left network.; otherwise You weren't in that network.
Leaving stops the two-way sharing at once. Copies of Network listings that can no longer be reached, both peer listings posted in this server and your own listings posted on the peers, have their buttons removed and are replaced with This listing is no longer shared with this server. Public listings are left alone; they stay visible everywhere regardless of network membership.
The network itself keeps existing for its other members, even when the leaving server created it. This command does not check whether Group Finder is switched on for the server.