I've configured MC to "add to playing now (to end)" when I double-click a file.
Most of the time this works exactly the way I want: Music is played in the same order I add it to "playing now" and I don't have to use the right-click menus to "add to playing now". I can add new music while the list is being played without disrupting anything.
The only problem is that sometimes playing now runs out of files before I add a new file. Then I automatically double-click a new file to add it to the end, and MC starts over from the beginning of "playing now", usually playing a song I just heard a little while ago. Then I have to switch to "playing now" and double-click the file I just added, or press Ctrl-N a lot of times until I reach the right file.
Is there some kind of mode where playing now is seen more like a queue of files to be played, where MC would keep the old files at the beginning of playing now, but start playing the new files instead of restarting from the top of playing now? This would feel much more intuitive to me.