Maintain friendship to local classes in the local class include

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

Friendship for local classes
You do not maintain friendships between local classes on the
<ZK>Friends</> tab of the Class Builder.
To grant a local class access to the private components of a global
class, you must include the following statement in the definition
include of that local class:
CLASS <global_classname> DEFINITION LOCAL FRIENDS
<local_classname_1> <local_classname_2> .... <(>
<<)>local_classname_n>.
mit : <global_classname> : Name of the global class
<local_classname_1...n> : Names of the local classes to which
you want to grant friendship

Error message extract from SAP system. Copyright SAP SE.