I don't open 400 at once, they accumulate over time (I mostly open about 50-200 at once). And of course I am using tree style tabs, otherwise I would not be able to use more than 50 tabs efficiently (right now I have 71 opened, because I cleaned it up at the end of june). But that is not the point.

The arrow tab search does the exact same thing as using % modifier in the address bar. I still can't search pages that are in containers that are different from the currently opened site.