PreSonus StudioLive 24.4.2 - Manual (Page 139)

7 Studio One Artist Quick Start
7.6 Adding Virtual Instruments and Plug-in Effects to Your Song
StudioLive ™ Software Library
Reference Manual
135
The Mix button opens and closes the mixer window.
The Browse button opens the Browser window, which displays all of the
available virtual instruments, plug-in effects, audio files, and MIDI files,
as well as the pool of audio files loaded into the current session.