I dont believe you can add you own kind of metadata to a managed object the values look fixed
sap.ui.base.ManagedObjectMetadata.Kind = {
PROPERTY :0, SINGLE_AGGREGATION : 1, MULTIPLE_AGGREGATION : 2,
SINGLE_ASSOCIATION : 3, MULTIPLE_ASSOCIATION : 4, EVENT : 5
};
to access the metadata of an object you can use the getter getMetadata -eg
myControl.getMetadata();