In Cost plans, there are two views:
Investment Currency View
Billing Currency View
On selecting Investment currency view, a new row is added (combination of cost type, chargecode and transaction class).
Why is this row visible on a particular view (and is uneditable)?
Because CA PPM allows for multi-currency Configuration.
The Investment Cost Plan has two views. The 'Investment Currency View' allows the user to see the Planned Cost, Planned Revenue, Actual Cost and Actual Revenue with the investment currency code. This is the native amounts saved within the investment when the cost plan is created. The 'Billing Currency View' allows the user to see the Billing Planned Cost and Billing Planned Revenue with the billing currency code. The currency codes are automatically displayed in a multi-currency environment and cannot be removed from the configuration on the financial plan views or other system-restricted views.
Since the Billing currency view is showing in the billing currency and not the investment currency, I believe it would be non-editable.
For a more complete answer see TEC611169