What is this mysterious Lock?

Ok, I’m stumped

Hasn’t anyone figured this out yet?

Lol. Makes sense.

When the library is expanded it will auto collapse once you load a song (bringing back the waveform and controls). If the lock is activated, however, then the library will stay up all the time (until you unlock by pressing the lock icon). So basically the lock allows you to quickly load one song after another with a single tap and is most useful during preparation.

Please let me know if this clarifies it. Also if you have any ideas on how to make this feature more obvious, I’d love to hear your thoughts.