So, to be clear, I do understand that I need to replace the playlist name with the one I have exported. I was simply using playlist1.m3u because that's the example you used.
If you export any playlist and call it using a command line this is what happens;
The music currently being played stops.
The new playlist loads in.
It does not play.
Also, to be clear, calling the playlist file, and associating m3u files with musicbee produced the same results.
I could create a batch file and make it play immediately or, as suggested, I could use autohotkey to create a macro but it's easier to just use my streamdeck to create a multi-action key. It doesn't get round the main issue though that it doesn't replicate the in program functionality where double-clicking on a playlist immediately cross-fades into that new playlist.
This is what I need really. Not a screeching halt followed by a load of new songs.
/queuenext doesn't work because it loads the music files in order and ignores shuffle functionality. So choosing the playlist would always play them in the exact same order each time.
Many thanks.