Below is a functional implementation of SQL Replication Monitoring. I understand that there will be a cleaner solution in future: https://www.netxms.org/forum/general-support/using-netxms-to-monitor-mysql-replication-status-and-progress/msg11314/#msg11314

However in the mean time;

agent config needs the following line;

ExternalParametersProvider=mysql -uuser --host=ipaddress -ppassword --execute "SHOW slave status\G" | sed 's/ //g;s/:/=/g;s/^/SqlSlave./':60

DCI Collection will be avaliable for all the slave status commands prefixed with SqlSlave. IE SqlSlave.Slave_IO_Running and SqlSlave.Slave_SQL_Running.

Hopefully will save some time for someone else trying to achieve the same