Unable to find variable : mysql-monitor_username in global_variables table in information_schema database in MySQL

I am trying to perform the initial configuration in proxysql and I found that while doing the Configure monitoring, I am unable to find the variable mysql-monitor_username in the global_variables table. The article says that we need to execute the update statement in the mysql database but I don't see that option existing already and I cannot make changes to the information_schema.global_variables table because basically that's a view. Can someone please help me here in completing this step? Reference Link : https://proxysql.com/documentation/ProxySQL-Configuration/