Open multiple aup3 files in one instance

I must be doing something wrong… I’m on Windows 10 with Audacity 3.7.1 and I want to open multiple aup3 files (or mp3 files if aup3 won’t work) in one instance of the program, in separate tracks. On youtube, I’ve seen many videos where people do this just by selecting “File”, then “Open” and then selecting multiple files at the same time. When I do the exact same thing, each file opens up in a different Audacity Window rather than one Audacity window with multiple tracks. How do I get the ‘open files as multiple tracks in one window’ behavior? I plan to join these tracks end-to-end, that’s not the problem part. The problem part is just opening them without getting multiple instances of the Window. There is probably some simple obvious step I am missing because I can’t find the answer to this anywhere, so everyone else must be doing something I am not.
Okay, I did find that drag-and-drop import works for multiple mp3 files (but not aup3 files), so I’ll edit each aup3 individually, then convert to mp3, and then import them in multiple tracks.

You need to use File > Import rather than using Open

Open is normally used for openeing Audacity projects, byut Audacity does let you use open on audio files too - BUT what that does is to open a project ror each file in turn and then do a hidden import of each audio file .

Peter