This functionality has been removed by SAP from EHP5 (SAP Note 1420281) onwards.However if you have access to SE37,executing function module SE16N_INTERFACE with the options I_TAB, I_EDIT and I_SAPEDIT activated and still maintain tables.
Note: Don't use direct standard tables editing on client production system it may cause inconsistency and lead to serious issues.
Thanks,
Qayyum Ahsan