I think it's possible. One problem that I have with Remembrancer, as well as all approaches based on the same basic idea of 'show the user a list of similar items', is that this is fundamentally guaranteed to be mostly useless because the user will already remember many similar items and have deliberately omitted them. Sometimes you will forget, and then it can be quite helpful, sure, but for the most part, this retrieval strategy is inherently limited.

What you really get serendipity is from re-encountering things you don't know or have forgotten. And we know how to predict if you have forgotten something: spaced repetition and the forgetting curve! To manufacture serendipity, you simply track 'flashcards' of important things, but optimize for the opposite of the normal spaced repetition goal: you want to review only things you are predicted to have forgotten by now.

https://gwern.net/note/statistic#program-for-non-spaced-repe...

Then, as a Remembrancer agent, you make it show preferentially items that are similar but you have probably forgotten. (The Remembrancer agent can be treated as a fraction of a review, on the grounds that even just showing you the title briefly can trigger serendipity and if it didn't provoke any reaction from you, then that is evidence it is not useful and that title should be downweighted and show up less.)

You can definitely engineer the chance for interesting things to happen by surrounding yourself with interesting people in interesting places, and it's highly recommended imho to do so.

People talked about this on HN earlier: https://news.ycombinator.com/item?id=25968751

The short end of it is something like: serendipity = work + telling people about the work

Similar to the system gwern mentioned in a sibling comment, I have implemented a "spaced inbox" system [1] that shows me old notes that I have written. The idea is to encourage me to keep adding to and refining ideas I have (but of course, the scheduling can be tweaked to only show notes that I am likely to have forgotten, as gwern suggests). Perhaps coincidentally, both my spaced inbox system and the Remembrance Agent in the OP are designed to work with Emacs (though mine does not force the user to use Emacs).

[1]: https://github.com/riceissa/spaced-inbox

Consider an alternative view, that coincidence is an immutable feature of reality that can be searched. In that case, you aren't necessarily engineering coincidence. Rather you are searching with the intent to align your own actions with the inherent coincident bias of the universe.