I am guessing S is solo and M is Mute.
What do B and R buttons do?
C S P L ?
I need to get started on those tooltips 😀
B is for bounce, R is for record (arm/enable)
C = Cursor
S = Segment
P = Punch In/Out
L = Loop
Right click in the time ruler to get a menu with more descriptive text for CSPL.