Route 53 error: 'A record with the specified name already exists.'

When creating a new TXT record in Route53, the following error may appear:

Error occurred
A record with the specified name already exists.
(InvalidChangeBatch 400: Tried to create resource record set [name='mydomain.com.', type='TXT'] but it already exists)

The solution is to add the new value to your existing TXT record, because multiple values are supported:

1. Return to the ‘Records’ view for your Hosted Zone (to view existing records)
2. Select the existing TXT entry, then click ‘Edit’
3. In the ‘Value/Route traffic to’ text area, append the value for the new record you’re creating to this field
4. Click ‘Save changes’

Note the hint (as of this writing) below the ‘Value/Route traffic to’ field: ‘Enter multiple values on separate lines.’