Per Diem period dates (Start date and End date) edit/remove button is disabled

I need to change the end date of the previous period date of a per diem (and the start date of the latest period) but the edit/remove button is disabled. Where can I enable or edit it?

["As of January 2022" should be end dated on Nov 28 2022 and the latest period date should have a start date of November 29 2022.]