Please note I am NOT familar with the playlist function in xLights. However it is my understanding that xLights operates under ONE playlist and you make adjustments from there. I have also seen it mentioned that if you make a change, the playlist starts over. I use the playlist and Show On Demand in LOR just about every night that I am working traffic in front of my house. I have a dozen or more playlists. If traffic warrants I shorten the playlist. If "Let It Go" (for example) is requested and the traffic is still busy, I have a playlist for that. On the other hand if the song is requested and traffic is not busy, I have a playlist for that. The Show On Demand allows me to just bring that "Show" up and then click "Ok". The "Show" will play right after the current "Show" playing.
Maybe the request should be for "Shows" instead of "Playlists". Anyway, I think you understand my request.