You are able to add additional templates that affect indices that you don't manage directly.
Try putting this into Kibana dev tools:
PUT _template/custom_monitoring_template
{
"index_patterns": [
".monitoring-es-*"
],
"mappings": {
"properties": {
"index_stats": {
"properties": {
"shards": {
"properties": {
"total": {
"type": "long"
}
}
}
}
}
}
}
}
This will affect newly created indices, so it will not automatically start working until the next index is created (which will be tomorrow)