library filters: key and bpm relative to current track

Filters are really helpful for shortlisting a playlist to only the tracks you might want to play. In particular, I like using BPM and Key filters to show just tracks that are close to the current track. But as I shift key and tempo, the fixed filters no longer apply. It would be super helpful to be able to specify keys and bpm range relative to the current track, that way the filter will automatically keep the shortlist relevant and perfect. This would be technically very easy to implement, and a very nice workflow improvement.