There are two possible reasons:
1. If the intersection includes a DeptID that is planned for Inactivation, it will display as read-only to provide visibility but restrict additional planning.
You can learn more about DeptID Inactivation on the DFL Concierge website.
2. If the intersection includes an Account that is managed by the Central Budget Office (such as 71110 - General Allocation, 71295 - Other Central Commitments,
5380X - Fee Remission - Plan) it will display as read-only.