Like all advanced text editors and like the WikEd gadget, WikiEditor needs to remember the previously used search&replace strings. The users shouldn't have to type them again on every article they want to use them on.
Browsers automatically remember text entered into input boxes, so the question is how to make that work with WikiEditor's search and replace input boxes. They need to have name attributes, also maybe they need to be in a form (with onsubmit="return false;") and the Search and Replace buttons need to be Submit buttons. I haven't tested these yet.