If an object isn't specified in a <mapframe/>, an OSM relation could be automatically pulled from Wikidata (property P402) by using the Wikidata ID of the page, with an option to turn this off.
|Open||None||T145171 <maplink/frame> without lat/long should use coordinates from Wikidata|
|Declined||None||T145284 Allow Wikidata's P402 (OpenStreetMap Relation identifier) to be used in Kartographer|
Please, don't use Property P402 !!!
We show it on WIWOSM  project that we don't need it to link from Kartographer to an geometry in OSM.
We can use Wikipedia and Wikidata-Tags in OSM and are so more flexible to suport also points and lines without and relation-id. The relation ID's in OSM are not stable.
so please change Kartograher to support OSM data without P402.
We can't use OSM ids because they're not guaranteed to be stable, unlike Wikidata ids. We already have integration the other way around - with OSM's wikidata tag and will continue improving it.
I agree that it's not necessary to have the same information in both OSM and Wikidata, especially where P402 is (slightly) more likely to become inaccurate (e.g. when a transport service is deleted because it no longer exists and Wikidata isn't updated). I've started a deletion discussion here.
@Liuxinyu970226, please don't hijack this ticket and especially don't remove tags that are obvioulsy relevant. Feel free to create a separate ticket for the community wishlist item.