'@Metadata.allowExtensions: true' is missing

What causes this issue?

'@Metadata.allowExtensions' should be annotated at the view.

System Response

Without this annotation, a customer cannot refine settings like the
rendering (@UI) or the ranking definition (@Consumption.ranking) on view
level.

How to fix this error?

Add the annotation on header level of the view.

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.