Hi @raman021,
This plugin adds the JSON-LD schema.org markup for the “Google Sitelinks Search Box” but there is no markup to inform Google that you want sitelinks shown in the search results. So there can’t be a plugin to show them.
Here is more information about the sitelinks: Google Search Console Help: Sitelinks.
We only show sitelinks for results when we think they’ll be useful to the user. If the structure of your site doesn’t allow our algorithms to find good sitelinks, or we don’t think that the sitelinks for your site are relevant for the user’s query, we won’t show them.
At the moment, sitelinks are automated. We’re always working to improve our sitelinks algorithms, and we may incorporate webmaster input in the future. There are best practices you can follow, however, to improve the quality of your sitelinks. For example, for your site’s internal links, make sure you use anchor text and alt text that’s informative, compact, and avoids repetition.
So it’s up to Google to show sitelinks for your site. Traffic and SEO visibility are important signals for Google to show the sitelinks so you have to work on this.
Sorry that we can’t help you further.
Best regards form Spain.
