Update a scene's prompt or duration. EDIT-INVALIDATES-ASSET: changing the prompt of a generated scene resets it to pending and drops its footage (a stale render cannot survive a prompt edit) — say so before doing it. With ripple_secondary "shift" (the default) the other lanes follow the footage: time the scene loses at its start or end is cut from every lane at that edge, and time it gains is inserted there, so clips, captions and stickers stay over the frames they were placed on (one that spans that edge is split or stretched). "none" changes the main track alone. Refuses a shift that moves a locked track (unlock it with lock_track, or pass ripple_secondary "none").