Export a playlist to USB in Traktor.

Two usual causes. Native Instruments documents that with any Beatport or Beatsource LINK track loaded on a deck, exporting playlists with tracks as files to other locations and devices is unavailable due to licensing restrictions, so unload every streaming track first. The other cause is the wrong right-click target: the command lives on a playlist, while the Playlists root folder shows Import Playlist and a Smartlist shows Export Smartlist. WAV masters fill a stick fast. Where the booth does not need lossless, the WAV to MP3 converter shrinks them without uploading anything.

There is no direct handover, because the .nml file is a Traktor format. Export the playlist first, which gives you a folder of the actual audio files, then drag that folder into the crates view in Serato DJ Pro: a dropped folder instantly becomes a crate. Run Analyze Files afterward with Set Auto BPM and Set Beat Grid checked, since grids and cues do not travel. See export crates to USB in Serato.

No. Pioneer DJ players browse a drive that was exported from rekordbox, in either the conventional Device Library format or the newer OneLibrary format, and a folder of files next to an .nml means nothing to them. If you are playing on house players, prepare a second drive in rekordbox: export a playlist to USB in rekordbox walks through it.

In the Root Directory. Open Preferences, go to the File Management page, and look under Directories: Root Dir is the path to your Track Collection, Playlists, Settings, History and Mappings files. Copying that folder plus your music folders is a full library backup, which is a different job from exporting one list. See back up your DJ library.

Both. The manual is explicit: exporting a playlist creates a folder containing the tracks in the playlist as well as the playlist file. If tracks are missing from the exported folder afterward, they were already missing on disk before you started. Run Check Consistency on the Track Collection, relocate everything it counts under Tracks Missing, then export the playlist again.

Only from a Smartlist. The Smartlist context menu has Export Smartlist, which writes the list in M3U or NML format. A normal playlist gives you Export Playlist, which produces the folder of tracks plus a playlist file, or Save as Webpage, which writes an HTML running order and lets you choose the columns under List Options. More on Smartlists in Traktor.

Use the collection export. Right-click Track Collection, choose Export the Collection, leave the dollar symbol at the start of the Playlist Title alone, set Destination to your drive, select Copy Tracks To Destination, and confirm. On the new machine, right-click the Track Collection folder and select Import another Collection, then point it at the collection.nml on the drive.

Between two Traktor machines, largely yes. Traktor can write its own tags into the music files, controlled on the File Management page in Preferences by Only write custom Traktor tags and Write all tags to files, and the export copies those files. Into a different DJ app, no: it reads the audio and the standard tags, then builds its own beatgrids and cues from scratch.