Gadget export
To export the DuplicateReferences gadget, click on "Download" button, save the downloaded file, go to Special:Import on destination wiki and upload it. Then add the following to MediaWiki:Gadgets-definition page:
* DuplicateReferences[ResourceLoader|dependencies=wikibase.ui.entityViewInit|type=general]|DuplicateReferences.js|DuplicateReferences.css
You must have appropriate permissions on destination wiki (including the right to edit system messages) and import from file uploads must be enabled.