Watching a timeline and firing off changes one at a time is slow. Comments let you note everything as you watch, then hand the whole list to chat and get one revised timeline back.

Every comment also becomes a marker on the timeline, so you can see where your notes fall across the whole edit.

To show exactly what a comment is about, draw on the frame and attach the drawing to it.

To take the drawing off before you add the comment, click [Remove drawing]. When you click the comment later, its drawing shows over the preview at that frame. Drawings are sent to chat as pictures along with your comments.

When your notes are done, click [Send comments to chat]. Chat reads the whole list, proposes an edit plan covering every comment, and waits for you to confirm before it builds a new timeline.

Comments work for structural changes: assembly, storyline, cuts, pacing, and camera switches.

For audio levels, color, effects, and captions, it is usually quicker to work directly: use the Adjust tab, the Effects app, and the Captions app.

Comments attach to a timeline, so you need one open. If a synced timeline tab is open instead, the comment box is turned off and the panel shows "Create a timeline to leave comments." Switch to a timeline tab. Also check that the playhead is on a clip in the timeline.

You can, but the point of comments is to batch them. Chat handles the whole list in one plan, which usually gives a more coherent result than a run of separate requests.

No. Chat creates a new timeline with the changes applied, so the one you commented on stays as it was.