Don't let hitting the ESC key (or equivalent keys in other OS than Windows) close the quick filter bar.
From a usability standpoint it is realling annoying and bugging me for years that my quick filter bar disappears unintenionally on a regular basis and I have to reenable it often. Now I found out due to this topic, that it was caused by hitting ESC (on Windows) which closes the quick filter bar. A lot of users find this really annoying since the quick filter bar is a feature I and other users use on a regular basis (nearly every session).
Improvement of usability (and reduction of annoyment) since the quick filter bar does not keep disappearing unintentionally.