But it sounds like you are looking for a custom Ghost Admin that would query Wikidata wherever you used it's dynamic menu via typing `/` on a new line or just adding a new button on it's Ghost Admin editor toolbar so that when you highlight a word you would be given an option to do a Wikidata search that would then embed a
https://schema.org/sameAs statement or multiple other kinds of statements via a form to fill (in general, you can think of this as a custom link helper that optionally doesn't produce a link element but instead embeds the structured data).
Someone in the Ghost community could probably write a plugin or customize the Ghost Admin for you fairly easily to give you that feature. Ghost is all Javascript. ;-)