Clone Custom MetaData Records

Hi @Yalamanchili Naga Sajitha

, 

What’s wrong with the snippet 

• icadjust.clone() only copies the list in memory and discards the result. It doesn’t save anything.
• Setting c.Type__c = ... on a queried record only changes the in-memory copy. CMDT records can’t be updated or inserted with DML.
• [type.id](https://type.id/) is a paste artifact. It should be type.Id.

// 1. Query the source child records, including every custom field you want copied
List<child__mdt> source = [
    SELECT DeveloperName, MasterLabel, Type__c, Other_Field__c
    FROM child__mdt
    WHERE Parent__r.Label = 'Test record'
];
// 2. Get the target parent (the relationship value is based on DeveloperName, not Id)
Parent__mdt target = [SELECT DeveloperName FROM Parent__mdt WHERE Label = 'Test rec' LIMIT 1];
// 3. Build new CMDT records
Metadata.DeployContainer container = new Metadata.DeployContainer();
for (child__mdt c : source) {
    Metadata.CustomMetadata md = new Metadata.CustomMetadata();
    String newName = target.DeveloperName + '_' + c.DeveloperName;   // DeveloperName must be unique
    md.fullName = 'child__mdt.' + newName.left(40);                  // keep within the name length limit
    md.label = c.MasterLabel;
    // Reparent via the relationship field
    Metadata.CustomMetadataValue parentVal = new Metadata.CustomMetadataValue();
    parentVal.field = 'Parent__c';
    parentVal.value = target.DeveloperName;
    md.values.add(parentVal);
    // Copy the other fields
    Metadata.CustomMetadataValue typeVal = new Metadata.CustomMetadataValue();
    typeVal.field = 'Type__c';
    typeVal.value = c.Type__c;
    md.values.add(typeVal);
    // ...repeat for each remaining field
    container.addMetadata(md);
}
// 4. Deploy (asynchronous)
Id jobId = Metadata.Operations.enqueueDeployment(container, null);
System.debug('Deployment job: ' + jobId);

Things to watch 

• The deployment is asynchronous. Check progress in Setup > Deployment Status, or pass a Metadata.DeployCallback as the second argument to log success or failure.
• Query DeveloperName and MasterLabel, not just Id, since the deployment is keyed on fullName.
• The format for a metadata relationship value (plain parent DeveloperName versus ParentType__mdt.DeveloperName) is something I haven’t verified against your org. If the deploy fails with a relationship error, try the qualified form.
• This relationship field is technically a Metadata Relationship, not a true master-detail. It behaves similarly but doesn’t cascade-delete the same way.
• Run this in a sandbox first, then deploy to production through your normal path.

Easier no-code alternatives, if this is a one-off

• Export the 40 child rows via Workbench or Data Loader-style tooling. You can also retrieve them with sf project retrieve start -m CustomMetadata:child.*.
• Then copy and rename the .md-meta.xml files and update the parent reference.
• Redeploy with sf project deploy start. This is often the fastest option for a small, one-time copy.

 I hope you find the above information helpful. If it does, please mark it as Best Answer to help others too.