Yes, there is a way to set the email template on a custom record in SuiteScript 2.0. You can use the following steps:

1. Load the custom record using the N/record.load() method.
2. Set the emailTemplate property of the record to the internal ID of the email template that you want to use.
3. Save the record using the N/record.submit() method.

For example, the following code snippet shows how to set the email template for a custom record with the internal ID of 12345:

const record = N/record.load({
  type: 'customrecord_my_custom_record_type',
  id: 12345
});

record.emailTemplate = 54321; // Internal ID of the email template

N/record.submit(record);

You can also use SuiteScript to set the email template for a custom record on creation or update. For example, the following code snippet shows how to set the email template for a custom record when it is created:

const record = N/record.create({
  type: 'customrecord_my_custom_record_type',
  defaultValues: {
    emailTemplate: 54321 // Internal ID of the email template
  }
});

N/record.submit(record);

Or, you can use SuiteScript to set the email template for a custom record when it is updated:

const record = N/record.load({
  type: 'customrecord_my_custom_record_type',
  id: 12345
});

if (!record.emailTemplate) {
  record.emailTemplate = 54321; // Internal ID of the email template
}

N/record.submit(record);

By using SuiteScript to set the email template for a custom record, you can automate the process and save yourself time.