I made this browser extension that adds a section for related submissions automatically. The results are displayed in a sidebar right in the page's layout using HN native style just like other elements. I paid special attentions to UX to make it intuitive and seamless and now the extension is just part of the HN experience for me.

Implementation-wise, it integrates HN algolia search API and uses the submission title as its initial query with the ability to change the query and other options interactively.

It's available on: Chrome, Firefox, and as a userscript.

I shared it earlier last year when it was barely a prototype, at the time wasn't yet published and was only for chrome (hence the update): https://news.ycombinator.com/item?id=36102610. I've been using it daily since and I'm happy to share it now for you to give it a try.