Its not as easy to code as might be imagined, mainly due to the fact that settlement names can have multiple words in them, and various other issues that crop up. It is in fact harder to deal with than unit names was and that was a royal pain in the ass.
Added that feature.Pre-select the previous search string when the popup comes up. I want to be able to start typing without having to hit Ctrl-A del every time I search for a new string.