I blocked Wikipedia and boosted certain encyclopedias like Britannica and Brockhaus, but especially Brockhaus usually does not appear in the search results at all, even when I set it on 'pinned' in my personalized results settings. I assume this is because Kagi only gets access to (for example) Google's top 100 results and if they do not contain a Brockhaus result it can not be pinned, of course.
I found a "hack" to resolve this for me: I boost those domains I want boosted and additionally create a lens which looks like this "*, brockhaus.de, britannica.com" etc.
This seems to force include these domains in the search results and I get what I want, but I believe Kagi could offer a force inclusion in the personalized results settings or something.
