Thank you. Unfortunately, the Firefox Search Box is off-limits for add-ons right now, that is where the SearchWP developers gave up and the point of my work-around.

Would you find it feasible to go via right-click/Properties to change a keyword? A direct (quick and dirty) way would be to change the javascript under "Location", I could put a variable for the keyword in front of that code. The more accessible "Name" property is much more difficult to use (a background vs. content script issue) and I'm hesitant to look into that if you say that right-click/Properties was too cumbersome, anyway.

Another approach would be to insert fields into the actual web pages displayed in the tabs, maybe added space on top of each page (as long as they allow it, like some refuse the highlighting, too). But then, we would need another toggle bookmarklet, since I won't disfigure every single page with the key words ...