Delimiting dates in SM30

I created a custom 'Z' table with key fields including end date (ENDDA). The begin date (BEGDA) is the first field that is not a key field. When I click on the delimit button and enter a date to delimit the record, the previous record is delimited but the new record is not created. This process should delimit the existing record and create a new one, but instead there is only the delimited record. Isn’t this part of the SAP standard delimiting functionality? I’ve seen posted issues like mine but no resolutions. Any help would be appreciated.