Feature summary (what you would like to be able to do and where):
We do not have a way to say that a constraint should only apply when a property is used on a specific entity type. This is important because you may not want some constraints applying to other entity types like lexemes vs. items.
Use case(s) (list the steps that you performed to discover that problem, and describe the actual underlying problem which you want to solve. Do not describe only a solution):
I would like to use such a constraint qualifier to add the constraint below to property constraint (P2302) so that all properties used on items should have a type constraint.
Benefits (why should this be implemented?):
We can improve the data quality of Wikidata by recommending with constraints that all properties should have a defined ontological domain and range.