Delete a scene, clip, or sticker by id (captions soft-delete reversibly). Deleting a scene with ripple_secondary "shift" (the default) removes its span of time from every lane, so clips, captions and stickers over the scene go with it and everything after it moves earlier in sync; "none" closes the main track alone. A deleted clip still leaves its gap open whatever ripple_secondary says; ripple_delete closes it. Refuses a clip on a locked track, and a shift that moves a locked track (unlock it with lock_track, or pass ripple_secondary "none").