Records in Metadata Utility are by default locked. This is a safety measure to make sure that no data will be accidentally edited or deleted.
In order to ‘unlock’ a record, you can double click on the ‘Title’ to unlock the record. Alternative, you can also use the ‘Edit Record’ Button on the bottom to unlock the record as well.
Once you move to another record, Metadata Utility will automatically lock the Record(s) again.