You cannot add an actual date horizontal bar

What causes this issue?

You want to add an actual date horizontal bar to a network activity in
the diagram area of the project planning board.

System Response

You cannot set actual dates in this way.

How to fix this error?

If you want to set an actual date for a network activity, create a
confirmation.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.