This article is intended to described the expected behaviour of annotations configured on a Macro type variable
Macro Variable Annotations
The Macro type variable does not display annotations configured against it within the Service Catalog and has been designed this way.
This same behaviour is seen on the Service Portal as well, as it is meant to mimic what is seen on the platform.
If annotations are required on a Macro type variable, the best suggestion would be to use the Macro with label variable type. This will display the label (question) and annotations configured against it.