ALV-How to make the key fields editable while adding a new row

I have an ALV. I have to append a new row. Currently key fields are not editable. But these fields should be editable when I click the new row button?

While inserting a new row, I am getting an error each time. I have a field taskid in this table and the check table has two fields as primary key taskid and teamid. Is it the reason for this problem?