This functionality is in a gadget and community-maintained, not by the dev team.

I looked into this to find out what this function does. Here is what I currently assume:

• It uses the same API as https://www.wikidata.org/wiki/Special:ItemByTitle which searched by the title that the Article for an item has on another Wiki.
• that other wiki is Wikipedia in the language in which the user views the Wikidata interface: If you view it e.g. in German, it uses dewiki and uses the titles of German Wikipedia articles to link you to their corresponding Wikidata items. (…so there is some indirection (Other Wikipedia as title source, implicit Wikipedia selection via Wikidata interface setting) involved to understand it.)

• I do not know why users prefer this search, but I assume it can be more predictable than the "normal" search, since it only considers titles (but titles of a specific Wikipedia). It also might be useful for people switching between "their" Wikipedia and Wikidata (as they can transfer familiarity from their Wikipedia to Wikidata).
• The description on the gadget page is "search form to find an item directly by its sitelink", which I found a bit irritating, since one item can have many sitelinks.

Hey, @Lydia_Pintscher. Thanks for your comment. What are the implications of this being a widget when it comes to unbreaking the main search in Vector 2022? How might we proceed?

The UX team just had a co-design session to try to come up with potential solutions for this issue: you can find some ideas in this Figma file. As you'll see, some of these solutions involve:

• Making the sitelink search available directly in the new Wikidata header (e.g. adding an extra input)
• Integrating the sitelink search functionality within the search component (e.g. letting users switch between search modes using a dropdown search button)
• Providing a link to the Special:ItemByTitle besides or under the main search input
• Hiding this functionality: just make it available from the Special:Search page

We were hesitant about solutions like the first two listed, knowing that WMDE are not the maintainers of this feature. Maybe getting some usage data might help guide a decision here.

Notes from conversation with Lydia:

• We should reach out to the creators of the gadget and explain the situation to them
• We should request a fix of this production bug from them: the recommendation from WMDE would be to disable the gadget in the new Vector 2022 skin
• We need to let them know that the sitelink search capabilities would potentially be reincorporated to the WD search in future efforts to improve this feature

As per Lydia's suggestion, I'd like to request @Mohammed_Sadat_WMDE's support and facilitation of the exchange with the memebers of the community that are maintaining this gadget. Please feel free to reach out in case further information is needed. Thank you!