追加编辑Append Edit

叠加编辑（Append Edit）是把新片段放到现有轨道上方新轨道的操作——在剪辑页面用 Place On Top 完成，下层内容原样不动。

• 往高处放：新片段落在上方新建的轨道上，不覆盖、不推动下面的任何片段。
• 天生为 B-roll：盖住访谈跳剪、叠加画中画，画面换了、下面的声音照播。
• 配时间线入出点：先在时间线上圈好区域再叠，落点和长度一次到位（见 three-point-editing）。
• 上层遮下层：回放时上方视频轨道遮住下层画面，各轨道的声音独立播放。
• 不等于追加到末尾：Append at End 是另一个功能——把片段接到时间线最后一段之后，不叠轨。

An Append Edit places a new clip on a fresh track above the existing ones — in the edit page it's done with Place On Top, and everything below stays untouched.

• Up it goes: the new clip lands on a newly created track above, covering nothing and pushing nothing on the tracks below.
• Made for B-roll: cover jump cuts in interviews or layer picture-in-picture — the picture changes while the sound below plays on.
• Pairs with timeline In/Out: fence off a region on the timeline first, and the landing spot plus length arrive in one move (see three-point-editing).
• Top covers bottom: during playback the upper video track hides the picture below; audio from each track plays independently.
• Not Append at End: Append at End is a different function — it tacks the clip after the last one on the timeline, with no stacking.