Cache on playback

Hi there!,

Most if not all video editing software have some sort of caching mechanism to smooth out playback and save on processing power.

It would be tremendously useful to have something like that per track / event, I guess?, and only re-render specific parts when something on the chain has change.

btw, freezing is great, but freezing the entire track takes up to a few minutes most of the time, and just having to unfreeze to make a small change to then freeze again, will take anyone out of the creative zone.