Yes, some more options there would be nice, but it's part of the gecko engine.
Yet the above example is easy, just type
and since "kmeleon.pugins." is the beginning, and columns are sorted alphabetically, the hits are all together
What I will really have a problem with is gecko 1.9, there the filter shows not only matching pref names, but also if the filter word is only in the results, and no options for this :-(