I do not think it is possible anymore, Kibana expects the monitoring data to be in the .monitoring-* index.
This is a similar question where it is confirmed that you can't change: Change monitoring index name for Kibana UI
The currently recommended way to monitor the stack is to use metricbeat shipping the data directly to elasticsearch.
You can create a template for the monitoring index and add an alias lab-metricbeat so your ILM policy will still apply.