monitoring-8.x-1.x-dev/config/install/monitoring.sensor_config.core_maintenance_mode.yml

id: core_maintenance_mode
label: 'Maintenance mode'
description: 'Site maintenance mode'
plugin_id: state_value
value_type: 'bool'
category: 'Other'
status: TRUE
settings:
  key: 'system.maintenance_mode'
  value: FALSE