Hi Thad,
Some time ago I proposed the property exact match (P2888), which carries the same semantics as skos:exactMatch. There are efforts to but this property in good use. In this context it would only make sense to model all aspects of similarity mapping to Wikidata properties. I hope I am wrong, but I don't think a property matching skos:closeMatch, already exists. We could go forward and propose that property, similar to what I did with skos:exactMatch.
Since you are from
schema.org, I would love to see a discussion on all levels of matching between concepts and how to model that in Wikidata. i.e. should we also consider proposing skos:broadMatch.
Kind regards,
Andra