Well, the first thing to try is just this:
MCC_REFRESHmc20.exe /mcc 22007
Do that at the command line, and then see if the Playlist refreshes on the DLNA device. If that doesn't work, you could also try:
MCC_RELOAD_MC_VIEWmc20.exe /mcc 30000
Though I think the latter is likely to only apply to the currently active View in MC. If needed, we could conceivably use this combined with the ShowTreePath command line option to force the playlist to refresh, but let's avoid that if possible (because it involves switching the currently active view on your server copy of MC).
If neither work, I bet that
MCC_NOTIFY_PLAYLIST_FILES_CHANGED would. However, to do this you'll need to get the nPlaylistID number for your master playlist.
This is pretty easy. Open this page in your web browser on your MC server machine:
http://localhost:<PORT>/MCWS/v1/Playlists/ListMake sure to replace the "<PORT>" in the URL above with the port number set in MC's Options here:
Tools > Options > Media Network > Advanced > TCP PortThat will output an XML page that lists all the Playlists on your copy of MC, with their IDs for each one listed. Then, you should be able to do:
mc20.exe /mcc 34049,9580639
(which
should refresh playlist ID 9580639)
If none of the above works, then there are other things we can try. If you find one that works, you should be able to make a Scheduled Task in Windows that just runs the command on a repeating basis, so that it just refreshes periodically (however often you want).