I think this would need a property mapping a contest with the used
identifiers (basically, that table but in wikidata form).
So for instance,"Wiki Loves Monuments 2021 Sweden" could be defined as
including the "listed building in Sweden (Q328070)" and the "listed
historical ship in Sweden (Q16501309)", which use P1260 and P2317
identifiers respectively (whereas a few years earlier, maybe only Q328070
were included).
Cheers