Ability to "Freeze Pane" video / audio tracks in timeline
FCP7 allowed users to 'freeze' a number of video and/or audio tracks in their timeline, keeping them always in view even when they scroll down or up to see other tracks layers. This is extremely useful when doing mixing with lots of layers of audio (sounds effects and music), when you want to always be able to see the dialogue in A1 and be able to mix around it.
Jim Simon commented
I like the DaVinci Resolve method for handling this. In the Fairlight page, you can hide tracks. You still hear them, you just don't see them. This allows you to only see the track you're working on.