How can I append .mp3 (or .wav)files (one after another). I only see an “open” command and no “append” command. The object is to make one large file out of a dozen or so smaller files.
That’s a Feature Request. Audacity has no Import-Append.
The best bet is import them all and they stack up on their timelines. Then select each and Copy - Track-One - End - Paste.
If they’re all MP3s, you might be able to use one of the MP3 editors like MP3Split.