To add background to this request: we have recently had ~2400 deleted Wikidata items that were still used by SDC; many of these deletions have taken place years ago. It is super inconvenient to check whether an item is being used with SDC, thus practically no Wikidata admin includes this check in their deletion routine. This check needs to be made much much simpler.

Might want to widen this out to non-admins, who have fairly legitimate use cases for wanting to known which SDC items point at WD items and, come to mention it, which WP items have dependencies on WD items - such as by the use of templates having WD items as arguments. It's the sort of information to be expected at 'what links here', not reserved for admins.

I appreciate the point that admins may wish for an SDC prompt when deleting, but note that elsewhere WMDE are pointing to this ticket as the general purpose 'show SDC use of WD items', not merely the admin deleter's special case.

Being able to see Structured Data on Commons at Wikidata should be available to all editors. It should be shown when you click "WhatLinksHere" at Wikidata. When I am at Commons I can see where a document is used in Wikidata and Wikipedia. We need to see the same thing from Wikidata, not just during deletion.

Also once Wikidata item is deleted it should be removed from SDC, the way deleted image is removed from Wikidata or wikipedia. I just run into File:Francesco Filippini - Barche sulla spiaggia (1892-93).jpg which still references long deleted Q108176371 item. The item was deleted as part of removal of all contributions by some no-longer liked user, but it creates hard to fix mess on Commons.