Record the queue before and after the drop
Inspect the current playlist and identify the item being dragged. Note whether the existing entries disappear, the new item is appended or it appears next to play. These are different queue operations, even when each begins with the same file-manager gesture.
The stable manual says the automatic policy follows the underlying platform’s drag-and-drop information. It describes holding Shift as a typical append gesture, rather than an unconditional rule for every platform. Keep the operating system and any modifier key with the observation.
Inspect the explicit player policy
mpv’s drag-and-drop option includes replace, append and insert-next choices as well as automatic and disabled behaviour. An explicit value can therefore differ from a remembered operating-system convention. Check the active setting before concluding that the file manager or media source ignored the drop.
Choose the queue relationship that matches the task. Appending preserves earlier queued items and adds the new one later; inserting next expresses another order. Replacing is appropriate only when discarding the current queue is intended. Preserve a needed playlist before testing a replacement action.
Verify order without confusing source access
Use a small set of permitted local samples to compare the selected policy and actual queue. Confirm the resulting order, then check the next media item’s playback separately. A correctly appended entry can still fail to open, while a playable file can still have replaced a queue unintentionally.
For help, provide mpv version, operating system, active drag-and-drop value, modifier keys and playlist order before and after. Keep any private file locations redacted. These observations distinguish platform-supplied gesture information from an explicit player policy and prevent a queue-management event from being diagnosed as a failed or deleted media source.