I have several documents in various locations that I want to always be able to quickly access by typing their name in Krunner. Is there a way to favorite them, as you can favorite folders?

I can access them from the Recent list by typing a few characters from the name, and that's great. The problem is that the list of recents is very short (10? 20?) If I open a few photos one after another, my documents will fall out of the list of recents, even though I've accessed those documents far more times than each of the individual photos; the photos are simply more "recent".

BTW this highlights how naive the recency search is. I'd suggest implementing a "frecency" algorithm, the way web browsers do.