User pr0t0type made a tool that could toggle effects while notes are held down (bypassing an effect when the all notes go up). This works in the live midi context but would require a complicated and fragile setup to work on edited patterns (where it automatically writes to automation depending on notes written in the pattern).
It would be nice to have extended capabilities for the *Meta devices to be able to hook things to held states (so one could track noteon/noteoff on top of keys and velocity).
Or as a more general solution, if we could access to the currently held notes inside Formula scripts such ideas (and more) could be expressed there. It could work similar to trigger in pattrns map context.