Feature summary (what you would like to be able to do and where):

Wikidata should have a way for reusing references in statements (of a single item), like in wikitext (with ref names).
Presently, references in multiple statements are made by copying (there's DuplicateReferences gadget for it.)

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):

That's quote common problem.

Benefits (why should this be implemented?):

Data size savings; following DRY principle.