Record Delimiter can be changed in Details pane:
Click the first row in the Record pane of the Metadata Editor.
After that, there will appear record properties in the Details pane. Among them, there will be the Record delimiter property. Change this delimiter for any other value.
Such new value of the record delimiter will appear in the last row of the Record pane instead of the previous value of record delimiter. It will again be displayed grayish.
Remember that if you tried to change the record delimiter by changing the value displayed in the last row of the Record pane, you would not change the record delimiter. This way, you would only define other delimiter following the last field and preceding the record delimiter!