I've tried Qmmp audio player, and CoolPlayer+ audio player so far (from PortableApps).
In neither case was I able to:
1) associate mp3 file format files with the app.
2) configure it so that when I double clicked on an mp3 file, the file would enqueue into the existing list of mp3 files in the queue to be played.
So, I'm back to using my trusty portable Winamp for now (which can't do either of the above, either).
I use "Coffee" (https://www.portablefreeware.com/index.php?id=1317 ) to associate mp3 files with my portable Winamp app.
Your recommendations on one or more apps that can do the listed 2 things would be very welcome.
Thanks in advance!
(using Windows 10 Home here).