Proposed solution: Have an option that shows the nearby/"part of" items in the maps.
Who would benefit: Readers and editors that see a map on Commons and other wikis who then want to explore nearby items.
More comments: This proposal was also posted in the 2019 wishlist. Ideally this functionality could also be used in Special:Nearby to show a map of nearby objects rather than a list (As community-requested in 2017. Wikishootme is a current example where nearby Wikipedia articles and Wikidata items are shown on a map (along with Commons photos), but that is on the toolserver rather than built in to Mediawiki.