Preserve the current list before changing it
If dropping a file appears to erase the current playlist, record where it was dropped before trying again. The visible video area and playlist panel are different targets. Keep any valued playlist saved through the application’s supported route before using a test gesture.
Choose three short local samples with recognizable names. Open two as the starting list and use the third as the addition. This original example makes the expected result easy to inspect: an added third entry is different from a fresh list containing only the new file.
Use the documented playlist panel
The Celluloid README documents showing the playlist through its menu or F9. It distinguishes adding by dropping onto the playlist from replacing the list by dropping onto the video area. Open the panel and identify the actual target before releasing the test file.
Keep the list visible during the first comparison. A hidden panel can make a successful append look like no action if the currently playing item continues. Inspect the entries and order instead of relying only on whether the video picture changes.
Compare append and replacement intentionally
Drop the third sample onto the intended list area and inspect the resulting entries. Then use a separate saved or disposable list if you want to test replacement in the video area. Do not perform that second comparison against the only copy of a carefully arranged session.
Reorder one entry through the supported drag interaction and open it to verify which file was selected. Keep selection, ordering and playback as separate observations. A file can be correctly added but fail to open because its original location is unavailable, which is a later issue than the drop target.
Check the result before continuing playback
Confirm the final list contains the intended items in the intended order and restore the ordinary session if needed. If the gesture behaves differently, retain the package source, Celluloid version and exact target used. A custom desktop integration can introduce another handoff context worth recording.
The expected outcome is a predictable list edit. It does not copy the media into the application, make an unavailable network resource playable or certify that the playlist is permanently saved. Verify any cross-session persistence through the actual supported save and reopen workflow.
Questions answered
Why did the video-area drop replace my list?
Celluloid documents different drop targets. Use the playlist area for the documented append behavior.
Does adding a file copy it into Celluloid storage?
Treat a playlist item as a reference and verify the actual file access separately. A successful list edit is not a media backup.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.