You do not have delete authorization for group &

What causes this issue?

To delete planning parameters, you must have delete authorization for
authorization group &V1& defined for the planning parameters.

System Response

The authorization object for planning parameters is called G_820_GPL
and is made up of the authorization group and the activity, which has
the value 06 for delete authorization.

How to fix this error?

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.